Endoscope

ABSTRACT

An endoscope includes at least one lens having a circular exterior shape in a direction perpendicular to an optical axis, an image sensor that has a square exterior shape in the direction perpendicular to the optical axis, and has one side whose length is same as length of a diameter of the lens, a sensor cover that has a square exterior shape in the direction perpendicular to the optical axis, and has one side whose length is same as one side length of the image sensor, a bonding resin portion that fixes the sensor cover to the lens, the optical axis of the lens coinciding with a center of the imaging area.

BACKGROUND Technical Field

The present invention relates to an endoscope.

Description of the Related Art

In the related art, an endoscope, which captures an image of an internalorgan of a patient's body or an inside of equipment or a structure,comes into wide use in the medical field or the industrial field. Lightfrom an imaged site is imaged on a light-receiving area of an imagesensor in an insertion part of this type of endoscope, which is insertedinto an observed object, by an objective lens system. The endoscopeconverts the image forming light into electrical signals, and transmitsthe electrical signals, which are video signals, to an external imageprocessing apparatus or the like via a signal cable.

In an endoscope used in the medical field, it becomes important that athinner outer diameter of a distal insertion part inserted into the bodyof a patient is required so as to reduce a burden on the patient. In therelated art, typically, the maximum outer diameter of a peroralendoscope is approximately 8 mm to approximately 9 mm. For this reason,during insertion, the peroral endoscope may be likely to come intocontact with a tongue root, or may cause a patient to feel nausea ordyspnea. In recent years, a thin nasal endoscope quickly comes into wideuse. The maximum outer diameter of the thin nasal endoscope isapproximately one half of that of the peroral endoscope, that is, isapproximately 5 mm to approximately 6 mm. For this reason, the thinnasal endoscope can be inserted into the nose. In many cases, since themaximum outer diameter is approximately 5 mm, which is thin, the thinnasal endoscope less causes vomiting reflex, and the insertion of thethin nasal endoscope does not matter much.

An electronic endoscopic system 501 disclosed in WO2013/031276 andillustrated in FIG. 33 mainly includes an endoscope 503; a light sourcedevice 505; a video processor 507; and a monitor 509. The endoscope 503is configured to include a long and elongated insertion part 511; anoperation unit 513; and a universal cable 515 which is an electriccable. The insertion part 511 of the endoscope 503 is configured toinclude a distal portion 517, a curved portion 519, and a flexibletubular portion 521 which are disposed sequentially from a distal sideinserted into a patient. The operation unit 513 is configured to includean operation unit body 523, and a treatment tool channel insertionportion 525 through which various treatment tools are inserted into theinsertion part 511. A curve operation knob 527 is disposed in theoperation unit body 523 so as to curve the curved portion 519. The curveoperation knob 527 includes a UD curve operation knob 529 that curvesthe curved portion 519 in an upward and downward direction, and an RLcurve operation knob 531 that curves the curved portion 519 in arightward and leftward direction.

An endoscope 533 disclosed in WO2013/146091 and illustrated in FIG. 34includes an outer barrel 535 in a distal portion. An image mechanism 539is provided on the outer barrel 535, and is covered with a filling lightshielding material 537. The image mechanism 539 includes an image sensor543 including a light-receiving portion 541 on one surface thereof; acover member 545 that covers the surface on which the light-receivingportion 541 of the image sensor 543 is provided; a lens unit 547 that isoptically combined to the light-receiving portion 541 of the imagesensor 543; and a flexible printed wiring board 549. The lens unit 547includes an objective cover member 551; an aperture stop 553; aplano-convex lens 555; a plan-convex lens 557; and a lens barrel 559that fixes together these components which are disposed sequentiallyfrom an objective side. The plano-convex lens 557 is fixed to the covermember 545 with a bonding agent 561.

A further reduction in the outer diameter of an endoscope (for example,the thinning of the outer diameter of the distal insertion partdisclosed in WO2013/031276, or of an insertion part on the objectiveside disclosed in WO2013/146091) is required. The further reduction inthe outer diameter is based on such a medial demand that an operatordesires to insert an endoscope into a site (for example, a very thinduct or hole such as a blood vessel) of the body of a patient into whichit is difficult to insert existing thin nasal endoscopes including theaforementioned existing thin nasal endoscopes, and to observe the insideof the site in detail.

It is estimated from the exterior of the endoscope 503 (for example, aso-called flexible endoscope in which the insertion part 511 is flexiblesuch that the insertion part 511 can be inserted into a digestive organin the upper or lower part of a living body) illustrated in FIG. 1 anddescription of application examples in WO2013/031276 that the endoscope503 disclosed in WO2013/031276 is an endoscope which is inserted intomainly a digestive tract of a human body. For this reason, it isdifficult to insert the endoscope 503 into a very thin duct or hole suchas a blood vessel of a human body, and to observe the inside of the ductor hole via the endoscope 503.

In the endoscope 533 disclosed in WO2013/146091, the sizes of the imagesensor 543 and the flexible printed wiring board 549 of the imagemechanism 539 are larger in a radial direction than the outer diameterof the lens barrel 559. In addition, the endoscope 533 is configuredsuch that the outer barrel 535 accommodates the image mechanism 539including these members, and the image mechanism 539 is covered with thelight shielding material 537 with which the outer barrel 535 is filled.For this reason, a protrusion distance of the image sensor 543 and theflexible printed wiring board 549 which protrude outward from the lensbarrel 559 in the radial direction, and the thickness of the outerbarrel 535 are disadvantageous to a reduction of the size of theendoscope 533. Since the outer barrel 535 is required, the number ofcomponents increases, and the cost increases.

BRIEF SUMMARY

The present invention has an object to provide an endoscope with areduced size (for example, the thinning of the outer diameter of adistal insertion part) and a reduced cost.

According to an aspect of the present invention, there is provided anendoscope including: at least one lens having a circular exterior shapein a direction perpendicular to an optical axis; an image sensor thathas a square exterior shape in the direction perpendicular to theoptical axis, and has one side whose length is same as length of adiameter of the lens; a sensor cover that covers an imaging area of theimage sensor, has a square exterior shape in the direction perpendicularto the optical axis, and has one side whose length is same as one sidelength of the image sensor; a bonding resin portion that fixes thesensor cover to the lens, the optical axis of the lens coinciding with acenter of the imaging area; a transmission cable connected to the imagesensor; an illuminator provided along the lens and the transmissioncable; a tubular sheath that covers a portion of the illuminator and thetransmission cable; and a cover tube that covers the lens, the imagesensor, and a portion of the illuminator, is coaxially connected to thetubular sheath in a state that outer circumferential surface is flushand continuous with outer circumferential surface of the tubular sheath,and forms a distal portion. The cover tube is smaller in thickness thanthe tubular sheath, and the distal portion including the lens, theilluminator, and the cover tube has a maximum outer diameter of 1.8 mm.

According to an aspect of the present invention, there is provided anendoscope including a single lens having a square exterior shape in adirection perpendicular to an optical axis; an image sensor that has anexterior shape which is same as an exterior shape of the single lens, inthe direction perpendicular to the optical axis; a sensor cover thatcovers an imaging area of the image sensor, and has an exterior shapewhich is same as the exterior shape of the single lens, in the directionperpendicular to the optical axis; a bonding resin portion that fixesthe sensor cover to the single lens, the optical axis of the lenscoinciding with a center of the imaging area; a transmission cableconnected to the image sensor; an illuminator provided along the singlelens and the transmission cable; a tubular sheath that covers a portionof the illuminator and the transmission cable; and a molded portion thatcovers and fixes the single lens, the image sensor, and a portion of theilluminator, and forms a distal portion. The molded portion is coaxiallyand continuously connected to the tubular sheath, and the distal portionincluding the single lens, the illuminator, and the molded portion has amaximum outer diameter of 1.0 mm.

According to the present invention, it is possible to reduce the sizeand the cost of an endoscope.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a view illustrating an example of the entire configuration ofan endoscopic system including an endoscope of each embodiment.

FIG. 2 is a perspective view of a distal portion of an endoscope of afirst embodiment which is viewed from the front side.

FIG. 3 is a sectional view illustrating an example of the distal portionof the endoscope of the first embodiment.

FIG. 4 is a sectional view illustrating an example of a configuration inwhich a separation part of the endoscope of the first embodiment isfilled with bonding resin.

FIG. 5 is a perspective view of an image sensor which is viewed from therear side, which illustrates a state in which a transmission cable isconnected to a conductor connection part of the endoscope of the firstembodiment.

FIG. 6 is a front view illustrating an example of the distal portion inwhich light guides as an example of a illuminator are disposed.

FIG. 7 is a characteristic graph illustrating an example of arelationship between the thickness and the transmittance of a moldedpart.

FIG. 8A illustrates an example of a captured image in a case where thereis stray light.

FIG. 8B illustrates an example of a captured image in a case where thereis no stray light.

FIG. 9 is a characteristic graph illustrating an example of arelationship between the amount of addition of an additive to the moldedpart and the tensile strength of the molded part.

FIG. 10 is a table illustrating an example of a relationship between theamount of addition of the additive to the molded part and the resistancevalue and the light shielding coefficient of the molded part.

FIG. 11 is a sectional view illustrating an example of a configurationin which a thin wall sheath is connected to the distal portion.

FIG. 12 is a sectional view illustrating an example of the configurationof an optical lens group of a lens unit.

FIG. 13 is a table illustrating lens data which indicates the opticalcharacteristics of the lens unit illustrated in FIG. 12.

FIG. 14 illustrates an example of a captured image based on an actualmeasurement result on which ring-shaped stray light appears.

FIG. 15 is a measurement image obtained via simulation, which is acaptured image in which multiple beams of stray light appear.

FIG. 16A is a light beam trace diagram of upper stray light among beamsof scattered ring-shaped stray light.

FIG. 16B is a light beam trace diagram of beams of both side stray lightamong the beams of scattered ring-shaped stray light.

FIG. 16C is a light beam trace diagram of lower stray light among thebeams of scattered ring-shaped stray light.

FIGS. 17A and 17B show measurement images obtained via illuminancedistribution simulation which illustrates whether or not stray light iseliminated by providing a rough surface portion.

FIGS. 18A and 18B illustrate an example of captured images of an actualmeasurement result in which stray light is reduced by providing therough surface portion.

FIG. 19 is a perspective view of the distal portion of an endoscope of asecond embodiment which is viewed from the front side.

FIG. 20 is a sectional view illustrating an example of the distalportion of the endoscope of the second embodiment.

FIG. 21 is a sectional view illustrating an example of a state in whichthe lenses are directly attached to the image sensor via bonding resinin the endoscope of the second embodiment.

FIG. 22 is a perspective view of the image sensor which is viewed fromthe rear side, which illustrates a state in which the transmission cableis connected to the conductor connection part of the endoscope of thesecond embodiment.

FIG. 23 is a side view illustrating an example of the dimensions ofobjective cover glass, the lens, and sensor cover glass.

FIG. 24A is a view illustrating the configuration of a positionadjustment jig.

FIG. 24B is a side view when the lens unit is fixed to the image sensor.

FIG. 24C is a video when position alignment in X and Y directions isperformed.

FIG. 24D is a video when position alignment in a Z direction isperformed.

FIG. 25A is a view illustrating the configuration of a camera-mountedposition adjustment jig.

FIG. 25B is a side view when the lens unit is fixed to the image sensor.

FIG. 25C is a video when position alignment is performed via a secondcamera.

FIG. 25D is a video when position alignment is performed via a firstcamera.

FIG. 25E is a video when position alignment in the Z direction isperformed.

FIG. 26 is a sectional view illustrating an example of a distal portionof an endoscope of a third embodiment.

FIG. 27 is a sectional view illustrating an example of the distalportion of the endoscope in which the hardness of a sheath differs in astepwise manner.

FIG. 28 is a sectional view illustrating another example of a distalportion of an endoscope in which the hardness of the sheath differs in astepwise manner.

FIG. 29 is a sectional view illustrating an example of the distalportion of the endoscope in which the hardness of the sheath differs ina stepwise manner, that is, in three stages.

FIG. 30 is a sectional view illustrating another example of the distalportion of the endoscope in which the hardness of the sheath differs ina stepwise manner, that is, in three stages.

FIG. 31 is a table illustrating an example of hardness values atpositions on an insertion part.

FIG. 32 is a sectional view illustrating a configuration in which asmall-diameter extension portion is not formed in a mold.

FIG. 33 is a view illustrating the entire configuration of an electronicendoscopic system including an endoscope in the related art.

FIG. 34 is a partial sectional view illustrating the structure of an endportion of the endoscope in the related art.

DETAILED DESCRIPTION

Hereinafter, specific embodiments of an endoscope of the presentinvention will be suitably described in detail with reference to theaccompanying drawings. Unnecessary detailed description may be omitted.For example, detailed description of already well-known items orduplicated description of substantially the same configuration elementsmay be omitted. The reason for this is to avoid that the followingdescription becomes unnecessarily lengthy, and to help persons skilledin the art easily understand this disclosure. The accompanying drawingsand the following description are provided to help persons skilled inthe art fully understand this disclosure, and are not intended to limitthe concept described in the claims.

First, a basic configuration example common to the endoscopes of theembodiments will be described. A configuration example illustratesconfiguration elements that the endoscope of the present invention mayinclude. It is not excluded that the endoscope of the present inventionhas a configuration which is a combination of the followingconfiguration examples.

First Embodiment Basic Configuration Example

FIG. 1 is a view illustrating an example of the entire configuration ofan endoscopic system including the endoscope of each embodiment. FIG. 1is a perspective view illustrating the entire configuration of anendoscopic system 13 including an endoscope 11 and a video processor 19.

Directions referred in the description of the specification are asdefined in each drawing. An “upper side” and a “lower side” respectivelycorrespond to upper and lower sides of the video processor 19 placed ona horizontal surface. A “front (distal)” and a “rear side” respectivelycorrespond to a distal side of an insertion part 21 and a proximal side(in other words, video processor 19 side) of a plug portion 23 of anendoscope body (hereinafter, referred to as the “endoscope 11”).

As illustrated in FIG. 1, the endoscopic system 13 includes theendoscope 11 which is a medical flexible endoscope, and the videoprocessor 19 that performs well-known image processing on captured stillor moving images of the inside (for example, blood vessel of a humanbody) of an observed object.

The endoscope 11 extends substantially in a forward and rearwarddirection. The endoscope 11 includes the insertion part 21 inserted intothe observed object, and the plug portion 23 connected to a rear portionof the insertion part 21.

The video processor 19 includes a socket portion 27 that opens in afront wall 25. A rear portion of the plug portion 23 of the endoscope 11is inserted into the socket portion 27 such that the endoscope 11 iscapable of transmitting to and receiving electric power and varioussignals (video signals, control signals, and the like) from the videoprocessor 19.

The electric power and the various signals are guided from the plugportion 23 to a soft portion 29 via a transmission cable 31 (refer toFIG. 3 or 4) inserted into the soft portion 29. Image data, which isoutput from an image sensor 33 provided in a distal portion 15, istransmitted from the plug portion 23 to the video processor 19 via thetransmission cable 31. The video processor 19 performs well-known imageprocessing such as color correction and gradation correction on theimage data transmitted from the plug portion 23, and outputs theprocessed image data to a display apparatus (not illustrated). Thedisplay apparatus is a monitor apparatus including a display device suchas a liquid crystal display panel. The display apparatus displays animage (for example, image data illustrating the inner status of a bloodvessel of a human which is a subject) of a subject captured by theendoscope 11.

The insertion part 21 includes the flexible soft portion 29, the rearend of which is connected to the plug portion 23, and the distal portion15 that is continuous with a distal end of the soft portion 29. The softportion 29 has a length suitable for coping with various endoscopicexaminations, various endoscopic surgeries, and the like. The softportion 29 is configured by covering an outer circumference of aspirally wound thin metal plate with a net, and applying a coating tothe outer circumference covered with the net. The soft portion 29 isformed to have sufficient flexibility. The distal portion 15 isconnected to the plug portion 23 via the soft portion 29.

Since the endoscope 11 and an endoscope 111 of each embodiment to bedescribed below are formed to be thin, the endoscope 11 or 111 can beinserted into a thin body cavity. The thin body cavity is not limited toa blood vessel of a human body. The examples of the thin body cavityinclude the ureter, the pancreatic duct, the bile duct, and abronchiole. That is, the endoscope 11 or 111 can be inserted into ablood vessel, the ureter, the pancreatic duct, the bile duct, and abronchiole of a human body. In other words, the endoscopes 11 and 111can be used to observe lesions inside a blood vessel. The endoscopes 11and 111 are effective in identifying atherosclerotic plaque. Theendoscopes 11 and 111 can also be applied to cardiac catheterization viaan endoscopic observation. In addition, the endoscopes 11 and 111 areeffective in detecting a thrombus or atherosclerotic yellow plaque. Thecolor tone (white, light yellow, or yellow) or the surface (smooth orirregular surface) of an atherosclerotic lesion is observed. The colortone (red, white, dark red, yellow, brown, or mixed color) of a thrombusis observed.

The endoscopes 11 and 111 can be used in the diagnosis and treatment ofthe renal pelvis and ureter cancer or idiopathic renal bleeding. In thiscase, an operator can observe the inside of a ureter and the renalpelvis by inserting the endoscope 11 or 111 into the bladder from theurethra, and moving the endoscope 11 or 111 forward to the ureter.

The endoscope 11 or 111 can be inserted into the papilla of Vater whichopens in the duodenum. Bile is produced in the liver, and is dischargedfrom the papilla of Vater in the duodenum via the bile duct. Pancreaticjuice is produced in the pancreas, and is discharged from the papilla ofVater in the duodenum via the pancreatic duct. An operator can observethe bile duct or the pancreatic duct by inserting the endoscope 11 or111 via the papilla of Vater which is an opening portion of the bileduct and the pancreatic duct.

In addition, the endoscope 11 or 111 can be inserted into the bronchus.The endoscope 11 or 111 is inserted via the oral cavity or the nasalcavity of a clinical specimen (that is, patient) in a supine position.An operator inserts the endoscope 11 or 111 to the trachea through thepharynx and the larynx while viewing the vocal cords. The bronchusbecomes thin whenever the bronchus is bifurcated. An operator canconfirm the lumen of a subsegmental bronchus via the endoscopes 11 and111 having a maximum outer diameter Dmax of 2 mm or less.

Hereinafter, various configuration examples of the endoscope of a firstembodiment will be described. The endoscope 11 of each embodiment mayhave any configuration of first to twenty-sixth configuration examples.

FIG. 2 is a perspective view of the distal portion 15 of the endoscope11 of the first embodiment which is viewed from the front side. FIG. 3is a sectional view illustrating an example of the distal portion 15 ofthe endoscope 11 of the first embodiment. FIG. 4 is a sectional viewillustrating an example of a configuration in which a separation part 47of the endoscope 11 of the first embodiment is filled with bonding resin37. FIG. 5 is a perspective view of the image sensor 33 which is viewedfrom the rear side, which illustrates a state in which the transmissioncable 31 is connected to a conductor connection part 49 of the endoscope11 of the first embodiment.

FIG. 2 is a perspective view illustrating a configuration of the distalportion 15 of the endoscope 11 illustrated in FIG. 1. FIG. 3 is asectional view illustrating the configuration of the distal portion 15illustrated in FIG. 2. FIG. 4 is a sectional view illustrating theconfiguration of the distal portion 15 illustrated in FIG. 2 from whichmolded resin 17 is removed. FIG. 5 is a perspective view illustratingthe configuration of the image sensor 33 illustrated in FIG. 4 which isviewed from an opposite side of a lens unit 35.

First Configuration Example

The endoscope 11 of the first configuration example includes the lensunit 35 in which lenses are accommodated in a lens support member 39;the image sensor 33, the imaging area of which is covered with sensorcover glass 43; the bonding resin 37 with which the lens unit 35 isfixed to the sensor cover glass 43 in a state where the optical axes ofthe lenses coincide with the center of the imaging area; and thetransmission cable 31 including four electric cables 45 which arerespectively connected to four conductor connection parts 49 provided ona surface opposite to the imaging area of (surface on the rear side of)the image sensor 33.

Multiple (three in the illustrated example) lenses L1 to L3 formed of anoptical material (for example, glass or resin) and an aperture stop 51interposed between the lenses L1 and L2 are assembled into the lenssupport member 39 while being proximate to each other in the directionof the optical axis. The aperture stop 51 is provided so as to adjustthe amount of light incident to the lens L2 or L3. Only light passingthrough the aperture stop 51 can be incident to the lens L2 or L3. Theproximity means that one lens and the other lens are slightly separatedfrom each other so as to avoid scratches caused by contact between thelenses. The entire circumferences of the lenses L1 to L3 are fixed to aninner circumferential surface of the lens support member 39 with abonding agent.

The term “bonding agent” in the following description does not representonly a substance used to bond together surfaces of solid objects in astrict sense, but also, in a wide sense, represents a substance capableof joining together two objects, or a substance that acts as a sealingmaterial if the hardened bonding agent has high barrier propertiesagainst gas and liquid.

A front end and a rear end of the lens support member 39 arerespectively blocked (sealed) by the lens L1 and lens L3 such that air,moisture, or the like is not allowed to infiltrate into the lens supportmember 39. As a result, air or the like is not capable of escaping fromone end to the other end of the lens support member 39. In the followingdescription, the lenses L1 to L3 are collectively referred to as anoptical lens group LNZ.

For example, nickel is used as the metal material of the lens supportmember 39. Since nickel has a relatively high modulus of rigidity andhigh corrosion resistance, nickel is suitable as the material of thedistal portion 15. In an examination or a surgery using the endoscope11, preferably, the circumference of the lens support member 39 isuniformly coated with the molded resin 17, and a biocompatible coatingis applied to the distal portion 15 before the examination or thesurgery such that nickel of the lens support member 39 is not directlyexposed from the distal portion 15. Instead of using nickel, forexample, a copper nickel alloy may be used. Since a copper nickel alloyhas high corrosion resistance, the copper nickel alloy is suitable asthe material of the distal portion 15. The metal material of the lenssupport member 39 is preferably selected from materials which can bemanufactured via electroforming (electroplating). The reason for the useof electroforming is that a member manufactured via electroforming has adimensional accuracy of 1 μm or less (so-called submicron accuracy),which is a very high accuracy, and a variation in the dimensions of alarge number of manufactured members is small. Stainless steel (forexample, SUS316) may be used as the metal material of the lens supportmember 39. Stainless steel (also referred to as a SUS tube) has highbiocompatibility. It is considered that stainless steel is suitable asthe material of an endoscope inserted into a thin site such as a bloodvessel of a human body. The lens support member 39 is a very smallmember. Errors in inner and outer diameter dimensions affect the opticalperformance (that is, image quality of a captured image) of theendoscope 11. If the lens support member 39 is configured of aelectroformed nickel tube, it is possible to ensure a high dimensionalaccuracy in spite of a fact that the lens support member 39 has a smalldiameter. As a result, it is possible to obtain the endoscope 11 capableof capturing high quality images.

The lens support member 39 may be made of a sheet material other thanmetal. The lens support member 39 may be positioned when the opticalaxes of the lenses of the lens unit 35 coincide with each other. If thelens unit 35 is covered with the molded resin 17, the positions of thelenses relative to each other are fixed. For this reason, the lenssupport member 39 may be made of a material having low strength, a thinthickness, and a light weight compared to those of the material of abarrel used to support multiple lenses in the related art. As a result,this material is capable of contributing to the thinning of the distalportion 15 of the endoscope 11. It is not ruled out that the samemetallic barrel as that in the related art is used as the lens supportmember 39.

As illustrated in FIG. 5, the image sensor 33 is configured as an imagedevice such as a small charge coupled device (CCD) or a smallcomplementary metal-oxide semiconductor (CMOS) which has a square shapewhen the image device is seen from the forward and rearward direction.Light incident from the outside is imaged on an imaging area 41 of theimage sensor 33 by the optical lens group LNZ inside the lens supportmember 39. The imaging area 41 of the image sensor 33 is covered withthe sensor cover glass 43.

For example, the bonding resin 37 is configured of UV and thermosettingresin. The bonding resin 37 preferably has light transmittingproperties, and a refractive index close to that of air. If UV andthermosetting resin is used as the bonding resin 37, it is possible toharden an exterior surface portion of the bonding resin 37 viaultraviolet light irradiation, and it is possible to harden the insideof the filling bonding agent, which cannot be irradiated withultraviolet light, via a heat treatment. In a state where the opticalaxes of the lenses coincide with the center of the imaging area 41, thelens unit 35 is fixed to the sensor cover glass 43 with the bondingresin 37. As a result, the lens unit 35 is directly bonded and fixed tothe image sensor 33 with the bonding resin 37, that is, the lens unit 35is directly attached to the image sensor 33 via the bonding resin 37.The bonding resin 37 is a bonding agent, the heat treatment of which isrequired so as to obtain a final hardness, and the hardening of whichprogresses to a certain degree of hardness via only ultraviolet lightirradiation.

If a light emitting surface of the lens facing the sensor cover glass 43is a convex surface, in the endoscope 11, an edge portion 55, which isan annular end surface on the circumference of the lens, is bonded tothe sensor cover glass 43. In this case, outer circumferences of thelenses and an outer circumference of the lens support member 39 may besimultaneously fixed with the bonding resin 37. If the edge portion 55of the lens is bonded to the sensor cover glass 43, an air layer isprovided between the lenses and the image sensor 33. Since the air layeris provided between the lenses and the image sensor 33, it is possibleto improve the optical performance of the lenses. For example, it ispossible to increase a refractive index difference of light emitted fromthe lenses to the air layer, and it is possible to obtain power forrefracting light. Accordingly, optical design such as improving aresolution and increasing an angle of view becomes easy. As a result,the image quality of an image captured by the endoscope 11 improves.

The four conductor connection parts 49 are provided on a back surfaceside rear portion of the image sensor 33. For example, the conductorconnection part 49 may be formed of a land grid array (LGA). The fourconductor connection parts 49 are made up of a pair of electric powerconnection parts and a pair of signal connection parts. The fourconductor connection parts 49 are electrically connected to the fourelectric cables 45 of the transmission cable 31, respectively. Thetransmission cable 31 includes a pair of electric power cables which arethe electric cables 45, and a pair of signal cables which are theelectric cables 45. That is, the pair of electric power cables of thetransmission cable 31 are respectively connected to the pair of electricpower connection parts of the conductor connection part 49. The pair ofsignal cables of the transmission cable 31 are respectively connected tothe pair of signal connection parts of the conductor connection part 49.

As described above, in the endoscope 11 of the first configurationexample, the lens unit 35 and the image sensor 33 are fixed togetherwith the bonding resin 37 in a state where a predetermined distancebetween the lens unit 35 and the image sensor 33 is held. If the lensunit 35 and the image sensor 33 are fixed together, the optical axis ofthe lens unit 35 is position-aligned with the center of the imaging area41. The positions of the lens unit 35 and the image sensor 33 relativeto each other are aligned at a distance therebetween at which light,which is incident from a subject and passes through the lens unit 35, isfocused on the imaging area 41 of the image sensor 33. The lens unit 35and the image sensor 33 are fixed together after position alignmenttherebetween.

The separation part 47 (refer to FIG. 4) is formed between the lens unit35 and the image sensor 33 which are fixed together. If the positions ofthe lens unit 35 and the image sensor 33 are aligned relative to eachother, and are fixed together with the bonding resin 37, the shape ofthe separation part 47 is determined. That is, the separation part 47acts as an adjustment gap for position alignment between the lens unit35 and the image sensor 33. Even if the separation part 47 is filledwith the bonding resin 37, the adjustment gap is not lost. In thespecific dimensional example, the separation part 47 is adjusted betweenat least approximately 30 μm and approximately 100 μm. At this time, atolerance is ±20 μm. Accordingly, in this case, the minimum adjustmentgap becomes 10 μm which is the remainder.

After the separation part 47 becomes an adjustment gap, and positionalignment between the lens unit 35 and the image sensor 33 is complete,in the endoscope 11, the separation part 47 is used as a fixing space ofthe bonding resin 37. For this reason, the lens unit 35 can be directlyfixed to the image sensor 33. Accordingly, it is not necessary toprovide an interposed member such as a frame or a holder which isrequired to fix the lens unit 35 to the image sensor 33 in the relatedart. Since a frame, a holder, or the like can be omitted, the number ofcomponents is reduced, and a fixing structure becomes simplified. As aresult, it is possible to reduce the diameter of the distal portion 15of the endoscope 11. Also, in a case where a further reduction in thediameter of the distal portion 15 is attempted (for example, thethinning of the outer diameter of a distal insertion part is attempted),it is possible to configure the distal portion 15 with the minimumdimensions. In addition, it is possible to reduce component costs. Sincethe number of interposed components for fixing the lens unit 35 to theimage sensor 33 is small, it is possible to reduce man hours required toperform position alignment and fixing work, and it is possible to easilyperform position alignment with high accuracy. It is possible to reducemanufacturing costs, and to improve productivity.

In the endoscope 11, the transmission cable 31 including the fourelectric cables 45 is connected to the image sensor 33. Since thetransmission cable 31 includes the four electric cables 45, it ispossible to reduce both the size and the cost of the endoscope 11. Forexample, the transmission cable 31 may be configured to include lessthan four (for example, three) electric cables 45 due to a dispositionspace of the conductor connection parts 49 on the back surface side rearportion of the image sensor 33. In this case, if one signal cable isomitted, a captured image signal or a control signal transmitted fromthe video processor 19 has to be superimposed on an electric powerwaveform passing through the electric power cables. In this case, amodulation circuit, a demodulation circuit, or the like is required forsignal superimposition, and thus, the number of components increases,and the total cost increases. If signal cables dedicated to transmit andreceive various signals (captured image signal, control signal, and thelike) are used, it is easy to configure a circuit, but the dedicatedsignal cables are disadvantageous to the thinning of the endoscope. Incontrast, if the transmission cable 31 is configured to include morethan four (for example, five) electric cables 45, a disposition space ofeach of the conductor connection parts 49 on the back surface side rearportion of the image sensor 33 becomes narrow. In a case where theendoscope 11 including the distal portion 15 having the maximum outerdiameter of 1.8 mm or less is manufactured which will be describedlater, it is difficult to perform connection work via soldering, and itis difficult to manufacture the endoscope 11. As described above, sincethe transmission cable 31 is configured to include the four electriccables 45, this configuration is very effective in reducing both thesize and the cost of the endoscope 11.

Second Configuration Example

In the endoscope 11 of the second configuration example in theembodiment, the maximum outer diameter Dmax of the distal portion 15 maybe set to a range from 1.8 mm to a finite diameter equivalent to thediameter of a circumscribed circle of a substrate of the image sensor 33which can be obtained via dicing.

In the endoscope 11 of the embodiment, an image sensor, one side ofwhich has a dimension of 1.0 mm is used as the image sensor 33 having asquare section in a direction perpendicular to the optical axis. As aresult, the image sensor 33 has a diagonal dimension of approximately1.4 mm, and the maximum outer diameter Dmax of the endoscope 11including a light guide 57 (for example, having 150 microns ϕ) as anilluminator may be set to 1.8 mm or less.

As described above, since the maximum outer diameter Dmax is set to lessthan 1.8 mm, the endoscope 11 of the second configuration example can beeasily inserted into a blood vessel of a human body.

Third Configuration Example

In the endoscope 11 of the third configuration example in theembodiment, as illustrated in FIG. 5, the substrate of the image sensor33 is formed into a square shape, and the four conductor connectionparts 49 are disposed in a row along one side of the substrate of theimage sensor 33. Each one of the conductor connection parts 49 is formedinto a rectangular shape. The four conductor connection parts 49 aredisposed spaced from each other while long sides of the four conductorconnection parts 49 are parallel to each other. The four conductorconnection parts 49 are disposed in a central portion of the substrateof the image sensor 33. As a result, the conductor connection parts 49are spaced from a circumferential edge of the substrate of the imagesensor 33.

A conductor of each of the electric power cables and the signal cables,which are the electric cables 45 of the transmission cable 31, iscovered with an insulation coating. One transmission cable 31 is formedby disposing two sets of the four electric cables 45 on the right andleft sides and in two stages in the upward and downward direction, andbinding outer circumferences of the insulation coatings with an outercover. Each conductor includes a bent portion 53 that is bent in a Ushape along a longitudinal direction of the conductor connection part49. The electric cable 45 is in contact with the conductor connectionpart 49 in a state where the bent portion 53 is pre-formed. A distal endof the bent portion 53 of the electric cable 45 is connected to theconductor connection part 49 via soldering. The image sensor 33 and thetransmission cable 31 are covered with the molded resin 17. As a result,the conductor connection parts 49, the bent portions 53, the electriccables 45, and the outer cover of the transmission cable 31 are embeddedin the molded resin 17.

As described above, in the endoscope 11 of the third configurationexample, since the four conductor connection parts 49 can be disposed inthe central portion of the substrate of the image sensor 33 while beingparallel to each other, it is easy to form the conductor connectionparts 49. Since the conductors of the electric cables 45 arerespectively connected to the four conductor connection parts 49, whichare spaced from each other in one direction, via soldering, it ispossible to easily perform connection work. Since the conductorconnection parts 49 are disposed in the central portion of the substrateof the image sensor 33, it is possible to form the bent portion 53 ineach conductor. Since the bent portions 53 are embedded in and fixed toa molded part 65, it is possible to reduce the application of tension,which is applied to the transmission cable 31, to joint portions betweenthe conductors and the conductor connection parts 49 (in such a way asto work as a strain relief). As a result, it is possible to improveconnection reliability between the electric cables 45 and the conductorconnection parts 49.

Fourth Configuration Example

In the endoscope 11 of the fourth configuration example in theembodiment, an illuminator is provided along the lens unit. That is, theendoscope 11 of the fourth configuration example includes the lightguide 57 as an example of the illuminator. In the following description,the light guide 57 is exemplified as the illuminator. Alternatively, theilluminator may be an LED directly attached to an insertion distalsurface of the distal portion 15. In this case, the light guide 57 isnot required.

The light guide 57 is formed of one optical fiber 59. For example, aplastic optical fiber (POF) is preferably used as the optical fiber 59.The material of a plastic optical fiber is silicon resin or acrylicresin, and both a core and a clad of the plastic optical fiber is formedof plastic. The optical fiber 59 may be a bundle fiber that is obtainedby bundling together multiple optical fiber strands, and attachingterminal metal fittings to both ends of the optical fiber strands. Adistal end of the optical fiber 59 becomes a light emitting end surfaceof the distal portion 15, and a proximal end of the optical fiber 59 isconnected to the plug portion 23. For example, a light source is an LEDprovided in the socket portion 27 or the like. If the plug portion 23 isconnected to the socket portion 27, in the endoscope 11, light from theLED propagates through the optical fiber 59 of the light guide 57, andis emitted from the distal end of the optical fiber 59. In thisconfiguration, the optical fiber 59 may be configured as one opticalfiber from the light source to an illumination light emitting end, andit is possible to reduce an optical loss.

As described above, since the endoscope 11 of the fourth configurationexample includes the light guide 57, the endoscope 11 alone is capableof capturing an image of a dark site.

Fifth Configuration Example

FIG. 6 is a front view illustrating an example of the distal portion inwhich the light guides 57 as an example of the illuminator are disposed.The endoscope 11 of the fifth configuration example in the embodimenthas a configuration in which multiple light guides 57 as an example ofthe illuminator are provided in a circumferential direction of the lensunit 35. Four light guides 57 are provided equally spaced from eachother in the circumferential direction of the lens unit 35.

As described above, since the four light guides 57 are provided equallyspaced from each other in the circumferential direction of the lens unit35, the endoscope 11 of the fifth configuration example is unlikely tocast a shadow to the upper, lower, right, and left sides of a subject.As a result, the endoscope 11 is capable of capturing a clear image incomparison with that captured by an endoscope including one light guide57 or two light guides 57.

Sixth Configuration Example

In the endoscope 11 of the sixth configuration example in theembodiment, the image sensor 33 is formed into a square shape. Theoptical fiber 59 of each of the four light guides 57 are disposed atsubstantially the center of each side portion of the substrate of theimage sensor 33 in a space interposed between the substrate of the imagesensor 33 and the circumscribed circle of the substrate of the imagesensor 33.

As described above, in the endoscope 11 of the sixth configurationexample, it is possible to effectively use a space interposed betweenthe square image sensor 33 and the circular molded part 65 substantiallycircumscribed to the image sensor 33. It is possible to easily disposemultiple (particularly, four) optical fibers 59 without increasing theouter diameter of the distal portion 15. As a result, it is possible toeasily manufacture the endoscope 11 without increasing the outerdiameter of the distal portion 15. The endoscope 11 is capable ofcapturing a clear image.

Seventh Configuration Example

In the endoscope 11 of the seventh configuration example in theembodiment, at least a portion of the lens unit, the image sensor, aportion of the transmission cable, and a portion of the illuminator arecoated with and are fixed by molded resin. The molded part 65 isconfigured of a molded resin material containing an additive such thatlight transmittance can be set to 10% or less.

FIG. 7 is a characteristic graph illustrating an example of arelationship between the thickness and the transmittance of the moldedpart 65. FIG. 7 illustrates an example of the measurement oftransmittance in a case where carbon black as an additive is added to amolded resin material (epoxy resin). In FIG. 7, a dotted line with blackcircles illustrates a case in which 5% by weight (wt %) carbon black isadded, and an alternate one lone and two short dashes line with blackrhomboids illustrates a case in which 1% by weight (wt %) carbon blackis added.

If 5% by weight carbon black is added, the light transmittance is almostindependent of the magnitude of the thickness of the molded part 65.Even if the thickness is 30 μm or less, it is possible to obtain highlight shielding performance, that is, a light transmittance ofapproximately 0.5% (light shielding coefficient of 99.5%). If 1% byweight carbon black is added, the light transmittance increases as thethickness of the molded part 65 decreases. If 1% by weight carbon blackis added, and the thickness of the molded part 65 is 30 μm or greater,the light transmittance can be reduced to 8.0% or less. Accordingly, ifthe thickness T of the molded part 65 is set to 30 μm or greater, acondition of a light transmittance of 10% or less can be fullysatisfied. For example, if the thickness of the molded part 65 is set to50 μm or greater, a light transmittance of 4.5% or less is obtained in acase where 1% by weight carbon black is added, and a light transmittanceof 0.5% or less is obtained in a case where 5% by weight carbon black isadded. Therefore, the molded part 65 is capable of more reliablyshielding light.

If the light transmittance of the molded part 65 is 10% or less, animage unit including the lens unit 35 and the image sensor 33 is capableof capturing a good quality image that is not much affected by straylight. In a case where the light transmittance of the molded part 65 is6% or less, even if the image sensor 33 has a high sensitivity, it ispossible to prevent stray light from affecting the quality of an image.If the light transmittance is greater than 10%, a captured image isaffected by stray light, and has a defect.

FIG. 8A illustrates an example of a captured image in a case where thereis stray light. FIG. 8B illustrates an example of a captured image in acase where there is no stray light. If stray light occurs as illustratedin FIG. 8A, an annular blown out highlight occurs in a captured imagedue to stray light, and a clear image cannot be obtained. As illustratedin FIG. 8B, it is necessary to prevent the occurrence of stray light inthe image unit while the endoscope 11 is used.

If an additive added to the molded part 65, as in the exampleillustrated in FIG. 7, light shielding performance improves by theextent of an increase in the amount of addition (the content) of theadditive, and in contrast, the bonding strength of the molded part 65decreases. Accordingly, it is necessary to add an adequate amount of theadditive to the molded resin material according to the bonding strengthcharacteristic of the additive.

FIG. 9 is a characteristic graph illustrating an example of arelationship between the amount of addition of an additive to the moldedpart 65 and the tensile strength of the molded part 65. FIG. 9illustrates an example of the measurement of tensile strength in a casewhere carbon black as an additive is added to a molded resin material(epoxy resin). The tensile strength corresponds to the bonding strengthof the molded part 65. As illustrated in FIG. 9, if the amount ofaddition is 1% by weight, the tensile strength decreases by onlyapproximately 2.5%. If the amount of addition is 5% by weight, thetensile strength decreases by approximately 12%. If the tensile strengthdecreases by approximately 20%, the bonding strength of the moldedmember may not be sufficient. For this reason, in a case where carbonblack is added, the amount of addition of the carbon black is preferablyset to 5% by weight or less.

If a conductive material such as carbon black is used as an additive,electric resistance decreases by the extent of an increase in the amountof addition, and conductivity is added.

FIG. 10 is a table illustrating an example of a relationship between theamount of addition of the additive to the molded part 65 and theresistance value and the light shielding coefficient of the molded part65. FIG. 10 illustrates an example of the measurement of a resistancevalue and a light shielding coefficient in a case where carbon black asan additive is added to a molded resin material (epoxy resin). Theresistance value and the light shielding coefficient were measured inthree cases, that is, a case in which the amount of addition of carbonblack is zero (0% by weight), a case in which the amount of addition ofcarbon black is 1% by weight, and a case in which the amount of additionof carbon black is 5% by weight. The light shielding coefficient of themolded part 65 having a thickness of 50 μm was measured. In a case whereno carbon black is added, the resistance value is 1.8×1013 to 5.0×1013.In a case where 1% by weight carbon black is added, the resistance valueis 2.5×1013 to 3.0×1013, and the light shielding coefficient is 95% orgreater. In a case where 5% by weight carbon black is added, theresistance value is 3.5×1010 to 5.0×1010, and the light shieldingcoefficient is 99% or greater. The electric resistance value, in a casewhere 5% by weight carbon black is added, decreases by 1000 times thatin a case where 1% by weight carbon black is added. For this reason, itis necessary to add an adequate amount of the additive to the moldedresin material according to the conductive characteristic of theadditive and the required insulation characteristic of an internalconfiguration element (electronic circuit or the like) which is a sealedtarget.

If the electric resistance of the molded part 65 is small, leakagecurrent may occur in the conductor connection parts 49 connected to theimage sensor 33 and in the transmission cable 31, and the electriccharacteristics of the periphery of a signal processing unit of theimage unit may deteriorate. In contrast, in a case where staticelectricity occur in the image unit, it is possible to reduce the impactof electrostatic discharge, to prevent the flowing of excessive currentto the image sensor 33, and to prevent the electrostatic destruction ofthe image sensor 33 by imparting adequate conductivity to the moldedpart 65. That is, the imparting of adequate conductivity to the moldedpart 65 can be a countermeasure against a surge of the image unit.

As described above, in the endoscope 11 of the seventh configurationexample, since the resin material (the molded resin 17) of the moldedpart 65 contains an additive, it is possible to set the lighttransmittance of the molded part 65 to 10% or less, and it is possibleto reduce the thickness of the molded part 65. As a result, the imageunit of the endoscope 11 is capable of having a satisfactory lightshielding characteristic, and it is possible to reduce the size of theimage unit.

Eighth Configuration Example

As illustrated in FIG. 3, the endoscope 11 of the eighth configurationexample in the embodiment includes the lens unit 35 in which lenses areaccommodated in the lens support member 39; the image sensor 33, theimaging area 41 of which is covered with the sensor cover glass 43; thebonding resin 37 with which the lens unit 35 is fixed to the sensorcover glass 43 in a state where the optical axes of the lenses coincidewith the center of the imaging area 41; the distal portion 15, themaximum outer diameter Dmax of which is set to a range from 1.8 mm to afinite diameter equivalent to the diameter of the circumscribed circleof the substrate of the image sensor 33 which can be obtained viadicing; the molded part 65 in which at least a portion of the lens unit35 and the image sensor 33 are coated with and are fixed by the moldedresin 17; and a tubular sheath 61 that is formed to have the same outerdiameter as that of the distal portion 15 and covers at least a portionof the molded part 65.

In the following description, the same reference signs are assigned tothe same members or configuration elements, and description thereof willbe simplified or omitted. The endoscope 11 (refer to FIG. 3) of theeighth configuration example will be described in comparison with theendoscope 11 (refer to FIG. 11) of the tenth configuration example.

The sheath 61 is made of a resin material having flexibility. For thepurpose of imparting strength to the sheath 61, a single cable, multiplecables, a braided tensile strength cable may be provided on the innercircumferential side of the sheath 61. Examples of the tensile strengthcable may include an aramid fiber such as a poly-p-phenyleneterephthalamide fiber, a polyester fiber such as a polyarylate fiber, apolyparaphenylene benzobisoxazole fiber, a polyethylene terephthalatefiber, a nylon fiber, a thin tungsten cable, and a thin stainless steelcable.

Similar to the endoscope 11 (refer to FIG. 11) of the tenthconfiguration example which will be described later, in the endoscope 11of the eighth configuration example, the entirety of the image sensor33, at least an image sensor 33 side portion of the lens unit 35, aportion of the transmission cable 31, and a portion of the light guides57 are coated with and are fixed by the molded resin 17. The meaning of“at least” also includes a case in which the entire outer circumferenceof the lens support member 39 is covered with the molded resin 17. Themolded resin 17 covers the image sensor 33 and the lens unit 35, andcontinuously covers the separation part 47 therebetween. The distalportion 15 of the endoscope 11 of the eighth configuration example mayinvolve a radiopaque marker. As a result, it is possible to easilyconfirm a distal end position of the endoscope 11 of the eighthconfiguration example in radioscopy.

Similar to the endoscope 11 (refer to FIG. 11) of the tenthconfiguration example which will be described later, the endoscope 11 ofthe eighth configuration example includes a distal flange portion 63 inthe distal portion 15. For example, the distal flange portion 63 may beformed of stainless steel. The distal flange portion 63 is formed into acylindrical shape in which a large-diameter portion larger than a distalside is continuous with a small-diameter portion. The large-diameterportion of the distal flange portion 63 has the maximum outer diameterDmax (1.8 mm). Insertion holes (not illustrated) for the insertion ofthe four optical fibers 59 are provided in the large-diameter portion,and the optical fibers 59 are respectively inserted into the insertionholes. An insertion hole (not illustrated) for the insertion of the lensunit 35 is provided in the small-diameter portion, and the lens unit 35is inserted into the insertion hole. The distal flange portion 63coaxially holds the lens unit 35. A fiber holding hole 67 for holding adistal side of the optical fiber 59 is drilled in the large-diameterportion of the distal flange portion 63 such that the fiber holding hole67 is positioned outward from the small-diameter portion. Four fiberholding holes 67 are provided equally spaced from each other in thecircumferential direction. The distal side of the optical fiber 59 isinserted into the fiber holding hole 67, and the optical fiber 59 isdrawn rearward along the small-diameter portion.

In the endoscope 11 of the eighth configuration example, when theoptical fiber 59 is positioned rearward from the distal flange portion63, the optical fiber 59 is disposed inside a cover tube 69 (refer toFIG. 3). The cover tube 69 is formed to have the same outer diameter asthat of the distal flange portion 63. The cover tube 69 is formed of amaterial such as metal or resin. A distal end of the cover tube 69 is incontact with the large-diameter portion of the distal flange portion 63.The cover tube 69 has the total length such that at least a rear end ofthe cover tube 69 reaches the transmission cable 31. The inside of thecover tube 69 is filled with the molded resin 17. That is, in theendoscope 11 of the eighth configuration example, the molded part 65 iscovered with the cover tube 69. The endoscope 11 of the tenthconfiguration example has the same configuration as that of theendoscope 11 of the first configuration example, apart from the factthat the cover tube 69 is omitted, and a distal end of the sheath 61 isin contact with and is bonded to a rear end of the distal flange portion63 with a bonding agent (refer to FIG. 11).

The molded part 65, with which the cover tube 69 is filled, includes asmall-diameter extension portion 71 (refer to FIG. 3) that extendsrearward from the rear end of the cover tube 69. The small-diameterextension portion 71 is molded into a columnar shape, and the fouroptical fibers 59 are embedded in the small-diameter extension portion71. The transmission cable 31 is embedded in the small-diameterextension portion 71 while being positioned inside the four opticalfibers 59. An inner diameter side of the sheath 61 is fixed to an outercircumference of the small-diameter extension portion 71 with a bondingagent or the like. That is, in the endoscope 11 of the eighthconfiguration example illustrated in FIG. 3, the distal flange portion63, the cover tube 69, and the sheath 61 are coaxially continuous witheach other with the maximum outer diameter Dmax set to 1.8 mm. In theendoscope 11 of the tenth configuration example illustrated in FIG. 11,the distal flange portion 63 and the sheath 61 are coaxially continuouswith each other while having the maximum outer diameter Dmax of 1.8 mm.

As described above, in the endoscopes 11 of the eighth configurationexample and the tenth configuration example, since at least a portion ofthe lens unit 35, the image sensor 33, and a portion of the transmissioncable 31 are coated with and are fixed by the molded resin 17, thenumber of interposed members required to fix the lens unit 35 to theimage sensor 33 is small. Accordingly, it is possible to reduce thediameter of the distal portion 15 of the endoscope 11. Also, in a casewhere a further thinning of the distal portion 15 is attempted, it ispossible to configure the distal portion 15 with the minimum dimensions.In addition, it is possible to reduce component costs. It is possible torealize the endoscope 11 capable of capturing an image of a very thintarget lesion such as a blood vessel of a human body. As a result, it ispossible to reduce the size and the cost of the endoscope 11.

The molded resin 17 is continuously molded over the image sensor 33 andthe lens unit 35, thereby contributing to an increase in fixing strengthbetween the image sensor 33 and the lens unit 35. The molded resin 17increases the air tightness (that is, there are not many small gaps),the water tightness, and the light shielding properties of theseparation part 47. The molded resin 17 also increases the lightshielding properties when the optical fibers 59 for the light guides 57are embedded.

Since the molded resin 17 is molded over the light guides 57, the lightguides 57 act as a structural member in the distal portion 15 of theendoscope 11, and it is possible to improve connection strength betweenthe soft portion 29 and the distal portion 15 in the thin endoscope 11.When the distal portion 15 is viewed from an insertion side outermostsurface (refer to FIG. 6) of the distal flange portion 63, in theendoscope 11, a gap between the lens unit 35 and the insertion hole (notillustrated) (provided in the distal flange portion 63 in advance) forthe lens unit 35 is filled with the bonding resin 37, and gaps betweenthe optical fibers 59 and the four fiber holding holes 67, which areprovided in the distal flange portion 63 in advance corresponding to theoptical fibers 59 is filled with the bonding resin 37. For this reason,in the endoscope 11, there is no gap between the insertion hole or thefiber holding holes 67 and the members (that is, the lens support member39 and the optical fibers 59). In the endoscope 11, the distal flangeportion 63 is bonded to the cover tube 69, and the cover tube 69 isbonded to the sheath 61, or the distal flange portion 63 is bonded tothe sheath 61 with the bonding resin 37, and there is no gap between thedistal flange portion 63 and the cover tube 69, between the cover tube69 and the sheath 61, and between the distal flange portion 63 and thesheath 61 respectively. As a result, when the endoscope 11 is sterilized(that is, is cleaned) after use in an examination or surgery, it ispossible to reduce the amount of adherence of cleaning residuals such asunwanted liquid to the endoscope 11, and the endoscope 11 is capable ofproviding a high level of convenience from the perspective of sanitationwhen the endoscope 11 will be used in a next examination or surgery.

In the endoscope 533 in the related art disclosed in WO2013/146091, theaxial line of the distal portion is offset from the optical axis of thelens unit 547. For this reason, a distance to a subject is likely tochange according to the rotational angle of the distal portion, and itis difficult to stably obtain a good quality image. If the axial line ofthe distal portion is offset from the optical axis of the lens unit 547,the state of interference between a duct inner wall and the distalportion is changed according to the rotational angle of the distalportion, and particularly, when the endoscope 533 is put into a thinhole, operability deteriorates. In contrast, in the endoscope 11 of theeighth configuration example, the distal flange portion 63, the covertube 69, and the sheath 61 are coaxially continuous with each other, andin the endoscope 11 of the tenth configuration example, the distalflange portion 63 and the sheath 61 are coaxially continuous with eachother. As a result, it is possible to easily thin the endoscopes 11, tostably obtain a good quality image, and to improve ease of insertion.

Ninth Configuration Example

In the endoscope 11 of the ninth configuration example in theembodiment, the thickness of the sheath 61 can be set to a range from0.1 mm to 0.3 mm. The thickness of the sheath 61 is the same as the stepdimension of a stepped portion between the cover tube 69 and thesmall-diameter extension portion 71. The small-diameter extensionportion 71 is a portion that protrudes toward an opposite side of thelens unit 35 with the image sensor 33 interposed between thesmall-diameter extension portion 71. That is, one transmission cable 31is disposed at the center of the small-diameter extension portion 71,and the four optical fibers 59 are disposed outside the transmissioncable 31. As a result, it is possible to easily reduce the diameter ofthe small-diameter extension portion 71 compared to a portion of themolded part 65 in which the image sensor 33 is embedded. That is, sincethe sheath 61 has the same outer diameter as that of the cover tube 69,the degree of freedom in designing the wall thickness of the sheath 61improves.

As described above, in the endoscope 11 of the ninth configurationexample, since the thickness of the sheath 61 can be set up to 0.3 mm,it is possible to easily increase the tensile strength of the sheath 61.

Tenth Configuration Example

FIG. 11 is a sectional view illustrating an example of a configurationin which a thin-wall sheath is connected to the distal portion.

In the endoscope 11 of the tenth configuration example in theembodiment, the thickness of the sheath 61 can be set to 0.1 mm. If thethickness of the sheath 61 is set to 0.1 mm, the endoscope 11 may notrequire the cover tube 69 described in the endoscope 11 of the eighthconfiguration example. That is, in the endoscope 11 of the tenthconfiguration example, the wall thickness of the sheath 61 is set tosubstantially the same wall thickness (0.1 mm) of the cover tube 69, andthus, the sheath 61 is capable of covering a portion of molded part 65in which the image sensor 33 and the lens unit 35 are embedded. In theendoscope 11 of the tenth configuration example, the distal end of thesheath 61 is in contact with and is fixed to a rear end surface of thedistal flange portion 63 with a bonding agent or the like. A decrease inthe tensile strength of the sheath 61 caused by a thickness reductioncan be made up for by providing the aforementioned tensile strengthcable or the like in the sheath 61.

As described above, in the endoscope 11 of the tenth configurationexample, since the cover tube 69 is omitted, and the sheath 61 can be indirect contact with the distal flange portion 63, it is possible toreduce the number of components.

Eleventh Configuration Example

FIG. 12 is a sectional view illustrating an example of the configurationof the optical lens group LNZ of the lens unit.

The endoscope 11 of the eleventh configuration example in the embodimentincludes the lens unit 35 including the lens support member 39, a frontgroup lens and a rear group lens which are accommodated in the lenssupport member 39, and the aperture stop 51 disposed between the frontgroup lens and the rear group lens; the image sensor 33, the imagingarea 41 of which is covered with the sensor cover glass 43; a bondinglayer made of the bonding resin 37 with which an image side finalsurface of the rear group lens of the lens unit 35 is fixed to thesensor cover glass 43 of the image sensor 33; and the distal portion 15,the maximum outer diameter Dmax of which is set to a range from 1.8 mmto a finite diameter equivalent to the diameter of the circumscribedcircle of the substrate of the image sensor 33 which can be obtained viadicing. The endoscope 11 of the eleventh configuration example has astructure in which the image side final surface of the rear group lensand an image side end surface of the lens support member 39 are fixed tothe sensor cover glass 43 via the bonding layer made of the bondingresin 37. A focal length fF of the front group lens, a focal length fBof the rear group lens, a focal length fel of the entire optical systemincluding the front group lens, the rear group lens, the bonding layermade of the bonding resin 37, and the sensor cover glass 43, a totaloptical length OL equivalent to a distance from a subject side foremostsurface of the front group lens to an image side rear end surface of thesensor cover glass 43, and a metal back MB equivalent to a distance fromthe image side final surface of the rear group lens to a subject sidefront end surface of the sensor cover glass 43 are capable of satisfyingrelationships: fel/fF<0, fel/fB>0, and 7.0≤OL/MB≤1200.

In the lens unit 35, the first lens L1 acts as the front group lens, andthe second lens L2 and the third lens L3 act as the rear group lens. Thefirst lens L1 is a leading lens of the optical lens group LNZ, and thethird lens L3 is a final lens of the optical lens group LNZ. In the lensunit 35, a first surface (foremost surface) L1R1 and a second surfaceL1R2 of the first lens L1 are concave surfaces, a first surface L2R1 anda second surface L2R2 of the second lens L2 are convex surfaces, and afirst surface L3R1 and a second surface L3R2 (final surface) of thethird lens L3 are concave surfaces, which are disposed sequentially froma subject side toward an image side.

The aperture stop 51 is provided between the first lens L1 and thesecond lens L2, that is, between the front group lens and the rear grouplens. A gap between the second surface (final surface) (concave surface)L3R2 of third lens L3 and the sensor cover glass 43 of the image sensor33 is filled with the bonding resin 37, and a bonding layer is formedtherebetween.

FIG. 13 is a table illustrating lens data which indicates the opticalcharacteristics of the lens unit illustrated in FIG. 12. In FIG. 13,surfaces respectively correspond to the surfaces L1R1 to L3R2 of thefirst lens L1 to the third lens L3, the aperture stop 51, and thebonding layer (bonding resin 37), and the radius of curvature (mm), theconic coefficient, and the effective diameter (mm) of each surface areillustrated. The thickness (mm) represents a distance (thickness)between the optical centers of the corresponding surface and thefollowing surface in the direction of the optical axis. The refractiveindex and the Abbe number represents the refractive index and the Abbenumber of an optical member that forms the corresponding surface. Theouter diameter (outer diameters of the first lens L1 and the third lensL3) ϕ of the optical lens group LNZ is approximately 0.9 mm toapproximately 1.0 mm. The sensor cover glass 43 of the image sensor 33has a thickness of 0.4 mm.

The focal length fel of the entire optical lens group LNZ is 0.58 mm.The focal length fF of the front group lens (first lens L1) is −0.714.The focal length fB of the rear group lens (second lens L2 and thirdlens L3) is 0.481. If the total optical length OL of the optical lensgroup LNZ is assumed to be a length from the foremost surface (firstsurface L1R1 of the first lens L1) of the leading lens to the imagingarea (image side rear end surface of the sensor cover glass 43 of theimage sensor 33), the total optical length OL is 2.287 mm.

If the metal back MB is assumed to be a length from a peripheral portionend surface of the final surface (second surface L3R2 of the third lensL3) to the subject side front end surface of the sensor cover glass 43of the image sensor 33, the metal back MB is 0.04 mm. The metal back MBmay also be referred to as a back focus which indicates the roughness ofthe final surface of the final lens. The metal back MB is used as aparameter containing the back focus BF, and the metal back MB iscollectively described. As illustrated in FIG. 13, the thickness of thebonding layer at the optical center is 0.05 mm, and in contrast, thesecond surface L3R2 of the third lens L3 is a concave surface.Accordingly, the metal back MB equivalent to the length from theperipheral portion end surface of the second surface L3R2 to the frontend surface of the sensor cover glass 43 is shorter than the thicknessat the optical center.

fel/fF is −0.812, fel/fB is 1.206, and OL/MB is 38.12.

Relationships, that is, fel/fF<0, fel/fB>0, and 7.0≤OL/MB, aresatisfied.

The range of MB is 0.005 mm or greater and 0.250 mm or less.

The range of OL is 2.000 mm or greater and 6.000 mm or less.

Accordingly, 8.0≤OL/BF≤1200 is obtained. If 7.0≤OL/MB is combined withthis relationship, 7.0≤OL/BF≤1200 is obtained. The maximum MB is anumeral based on MB=0.005 mm in underwater near point observation, andthe minimum MB is a numeral based on MB=0.190 mm in aerial remote pointobservation.

More specifically, examples of aerial long-range observation include thetrachea and the laryngeal part. Examples of aerial short-rangeobservation include a segmental bronchus and a bronchiole. Examples ofunderwater long-range observation include the inside of the uterus andthe stomach. Examples of underwater short-range observation include thebladder, the inside of a coronary artery, a knee joint, and the hipjoint.

As described above, the endoscope 11 of the eleventh configurationexample can be used for a human blood vessel, it is possible to reducethe metal back MB with respect to the total optical length OL, and it ispossible to realize a structure in which the lens unit 35 is directlybonded to and is fixed to the sensor cover glass 43 of the image sensor33 via the bonding layer. It is possible to obtain a high-strengthstructure of the image unit which includes a small number of components,it is possible to realize a short focal length of an image lens, and itis possible to reduce the length and the size of the image lens. As aresult, it is possible to reduce the size and the cost of the endoscope11.

Twelfth Configuration Example

Similar to the endoscope 11 of the eleventh configuration example, inthe endoscope 11 of the twelfth configuration example, the image sidefinal surface of the rear group lens is a curved surface. A refractiveindex nbe of the image side final lens of the rear group lens is not thesame as a refractive index nad of the bonding layer in a case where therear group lens is fixed via the bonding layer.

As described above, in the endoscope 11 of the twelfth configurationexample, since the final surface of the rear group lens is capable ofhaving refractive power by forming the image side final surface of therear group lens into a curved surface, it is possible to increase theconvergence of light beams from a subject which pass through the lensunit 35. As a result, it is possible to reduce an aberration of the lensunit 35, and to improve a resolution. If the image side final surface ofthe rear group lens is formed into a concave surface, since it ispossible to increase the height of an image of a subject in the imagingarea 41, it is possible to further reduce the diameters of the lenses.

Thirteenth Configuration Example

In the endoscope 11 of the thirteenth configuration example, an Abbenumber ube of the image side final lens of the rear group lens is set tobe greater than 25, and the refractive index nbe of the image side finallens of the rear group lens is greater than 1.40 and less than 1.90 incomparison with those in the endoscope 11 of the eleventh configurationexample.

As described above, in the endoscope 11 of the thirteenth configurationexample, since the Abbe number ube of the image side final lens of therear group lens is set to be greater than 25, and the refractive indexnbe of the image side final lens of the rear group lens is greater than1.40 and less than 1.90, it is possible to reduce the chromaticaberration of magnification of the lens unit 35, and it is possible toset the chromatic aberration of magnification to be smaller than thepixel pitch of the image sensor 33. As a result, it is possible toreduce color bleeding in a peripheral portion of a captured image.

Fourteenth Configuration Example

Similar to the endoscope 11 of the eleventh configuration example, inthe endoscope 11 of the fourteenth configuration example, the subjectside foremost surface of the front group lens is a concave surface orconvex surface, and the amount of sag d of the concave surface or convexsurface and the lens outer diameter ϕ of the optical lens groupincluding the front group lens and the rear group lens satisfy arelationship, that is, −0.1<d/ϕ<0.1.

As described above, in the endoscope 11 of the fourteenth configurationexample, since the subject side foremost surface of the front group lensis a concave surface or convex surface, and the amount of sag d of theconcave surface or convex surface and the lens outer diameter ϕ of theoptical lens group including the front group lens and the rear grouplens satisfy the relationship, that is, −0.1<d/ϕ<0.1, it is possible toshape the foremost surface of the lens unit 35 close to a flat surface,and to reduce the amount of adherence of impurity to the endoscope inuse. If the subject side foremost surface of the front group lens isformed into a concave surface, since it is possible to increase theviewing angle (angle of view) of the lens unit 35, it is possible towiden the visual field of a subject, and to further reduce the diametersof the lenses.

Fifteenth Configuration Example

The endoscope 11 of the fifteenth configuration example in theembodiment includes the lens unit 35 in which the front group lens andthe rear group lens are accommodated in the lens support member 39, andthe aperture stop 51 is disposed between the front group lens and therear group lens; the image sensor 33, the imaging area 41 of which iscovered with the sensor cover glass 43; the bonding resin 37 with whichthe lens unit 35 is fixed to the sensor cover glass 43 in a state wherethe optical axes of the lenses coincide with the center of the imagingarea 41; and a rough surface portion 73 (refer to FIG. 4) that is formedin an outer circumferential surface of the rear group lens and preventsthe outer circumferential surface from totally reflecting lightpropagating through the rear group lens.

FIG. 14 illustrates an example of a captured image based on an actualmeasurement result on which ring-shaped stray light appears. FIG. 14 isa captured image 75 that is obtained by a proto endoscope correspondingto the endoscope illustrated in FIG. 4 which is inserted into thebronchus of an animal.

In a result of an actual measurement performed by the endoscope 11 ofthe fifteenth configuration example, it was confirmed that ring-shapedstray light 77 appeared in the captured image 75. In the process ofdevelopment of the endoscope 11, it was confirmed that stray lightoccurred in a case where the number of lenses accommodated in the lensunit was changed from a four-lens configuration (not illustrated) to athree-lens configuration (not illustrated). It was confirmed that theoutput level of stray light became more prominent (that is, a capturedimage became blurred) (refer to FIG. 14) in a case where a three-lensconfiguration was changed to a direct-attached three-lens configuration(refer to FIG. 4) in which the final lens is directly attached to thesensor cover glass 43 of the image sensor 33.

FIG. 15 is a measurement image obtained via simulation, which is acaptured image in which multiple beams of stray light appear. Accordingto simulation, it was confirmed that among beams of scatteredring-shaped stray light, ring-shaped upper stray light 79, beams ofring-shaped both side stray light 81, and ring-shaped lower stray light83 prominently appeared.

FIG. 16A is a light beam trace diagram of upper stray light among beamsof scattered ring-shaped stray light. FIG. 16B is a light beam tracediagram of beams of both side stray light among the beams of scatteredring-shaped stray light. FIG. 16C is a light beam trace diagram of lowerstray light among the beams of scattered ring-shaped stray light.

As a result of performing light beam tracing via simulation, asillustrated in FIG. 16A, the upper stray light 79 was prominentlyaffected by reflection of light from a portion 85 of the outercircumferential surface of the lens L3 and reflection of light from aportion 87 of the lens L3 which projected from the lens support member39.

As a result of performing light beam tracing via simulation, asillustrated in FIG. 16B, the beams of both side stray light 81 wereprominently affected by reflection of light from an inner diameter edge89 of the aperture stop 51, reflection of light from the portion 85 ofthe outer circumferential surface of the lens L3, and reflection oflight from the portion 87 of the lens L3 which projected from the lenssupport member 39.

As a result of performing light beam tracing via simulation, asillustrated in FIG. 16C, the lower stray light 83 was prominentlyaffected by reflection of light from the inner diameter edge 89 of theaperture stop 51 and reflection of light from the portion 85 of theouter circumferential surface of the lens L3.

According to the simulation illustrated in FIGS. 16A to 16C, almost alllight forming stray light is incident to the imaging area 41 of theimage sensor 33 by reflection of light from the portion 85 of the outercircumferential surface of the lens L3 and reflection of light from theportion 87 of the lens L3 which projected from the lens support member39. It was verified that beams of scattered stray light wereconsiderably affected by reflection of light from the portion 85 of theouter circumferential surface of the lens L3 and reflection of lightfrom the portion 87 of the lens L3 which projected from the lens supportmember 39 (light, which was reflected from the portion 87 of the lens L3which projected from the lens support member 39, passed through the edgeportion 55 which was an annular end surface on the circumference of thelens L3).

The outer circumferential surface of the lens L3 of the proto endoscopewas frost-glassed. That is, the rough surface portion 73 (refer to FIG.4) was provided so as to prevent the outer circumferential surface fromtotally reflecting light propagating through the rear group lens (lensL3).

FIGS. 17A and 17B show measurement images obtained via illuminancedistribution simulation which illustrates whether or not stray light iseliminated by providing the rough surface portion. FIGS. 18A and 18Billustrate an example of captured images of an actual measurement resultin which stray light is reduced by providing the rough surface portion.

In the endoscope 11 of the fifteenth configuration example, since theouter circumferential surface of the lens L3 is frost-glassed, lightreflected from the portion 85 of the outer circumferential surface ofthe lens L3 is reduced by a scattering effect of the rough surfaceportion (frosted glass surface) 73. In the simulation illustrated inFIGS. 17A and 17B and the actual measurement result illustrated in FIGS.18A and 18B, almost all of the upper stray light 79, the beams of bothside stray light 81, and the lower stray light 83 were reduced andeliminated.

As described above, in the endoscope 11 of the fifteenth configurationexample, since the rough surface portion 73 is provided on the outercircumferential surface of the lens L3, it is possible to eliminatealmost all beams of scattered ring-shaped stray light without adding aseparate light shielding member (black painted cylindrical body or thelike) on the outer circumference of the lens L3. As a result, it ispossible to reduce the size and the cost of the endoscope 11 whilepreventing the occurrence of stray light.

Sixteenth Configuration Example

In the endoscope 11 of the sixteenth configuration example, the surfaceroughness of the rough surface portion 73 is preferably set to a rangeof an arithmetic average roughness Ra from 0.1 μm to 10 μm in comparisonwith the configuration of the endoscope 11 of the fifteenthconfiguration example. The rough surface portion 73 can be obtained bygrinding the outer circumferential surface of the lens L3 with abrasivegrains. It was ascertained that if the roughness Ra was 0.1 μm or less,the rough surface portion 73 was close to a mirror surface, and strengthof reflected light tended to gradually increase. It was ascertained thatif the roughness Ra of the rough surface portion 73 was 10 μm orgreater, the ratio of a rough surface to a reflecting surface decreased,and thus, strength of reflected light tended to gradually increase.

As described above, in the endoscope 11 of the sixteenth configurationexample, it is possible to prevent the occurrence of stray light withouta cost increase by imparting the optimum roughness to the lens L3without the use of other members.

Seventeenth Configuration Example

In the endoscope 11 of the seventeenth configuration example, the roughsurface portion 73 may be formed in an end surface (the edge portion 55)surrounding an image light emitting effective surface of the image sidefinal surface of the rear group lens (lens L3) in comparison with theconfiguration of the endoscope 11 of the sixteenth configurationexample. Since the rough surface portion 73 is provided on the outercircumferential surface of the lens L3, it is possible to prevent theoccurrence of stray light in the endoscope 11. In addition, since therough surface portion 73 is also provided in the edge portion 55, in theendoscope 11, it is possible to further prevent the occurrence of theupper stray light 79, the beams of both side stray light 81, and thelower stray light 83 which cannot be completely scattered by the portion85 of the outer circumferential surface of the lens L3 and the portion87 of the lens L3 which projects from the lens support member 39.

As described above, in the endoscope of the seventeenth configurationexample, it is possible to further prevent the occurrence of stray lightby providing the rough surface portion 73 in the edge portion 55 of thelens L3 without using other members.

Second Embodiment

Hereinafter, the endoscope 111 of a second embodiment will be described.

FIG. 19 is a perspective view of the distal portion of the endoscope 111of the second embodiment which is viewed from the front side. FIG. 20 isa sectional view illustrating an example of the distal portion of theendoscope 111 of the second embodiment. FIG. 21 is a sectional viewillustrating an example of a state in which the lenses are directlyattached to the image sensor via the bonding resin in the endoscope ofthe second embodiment. FIG. 22 is a perspective view of a side of theimage sensor which is opposite to the lens unit, which illustrates astate in which the transmission cable is connected to the conductorconnection part of the endoscope of the second embodiment. In the secondembodiment, the same reference signs are assigned to the same members asthose in the first embodiment, and duplicated description will beomitted.

Eighteenth Configuration Example

In the endoscope 111 illustrated in FIG. 19, the maximum outer diameterDmax of the distal portion 15 illustrated in FIG. 20 may be set to arange from 1.0 mm to a finite diameter equivalent to the diameter of thecircumscribed circle of the substrate of the image sensor 33 which canbe obtained via dicing.

In the endoscope 111 of the embodiment, an image sensor, one side ofwhich has a dimension of 0.5 mm is used as the image sensor 33 having asquare section in the direction perpendicular to the optical axis. As aresult, the image sensor 33 has a diagonal dimension of approximately0.7 mm, and the maximum outer diameter Dmax of the endoscope 111including the light guide 57 (for example, having 50 microns ϕ) as anilluminator may be set to 1.0 mm or less.

As described above, since the maximum outer diameter Dmax is set to lessthan 1.0 mm, the endoscope 111 of the eighteenth configuration examplecan be more easily inserted into a blood vessel of a human body.

Nineteenth Configuration Example

In the endoscope 111 of the nineteenth configuration example in theembodiment, as illustrated in FIG. 22, the substrate of the image sensor33 is formed into a square shape, and the conductor connection parts 49are disposed at four corners of the substrate of the image sensor 33.Each one of the conductor connection parts 49 is formed into a circularshape. Since the four conductor connection parts 49 are disposed at thefour corners of the square shape, the four conductor connection parts 49can be disposed while spaced the maximum distance from each other.

A conductor of each of the electric power cables and the signal cables,which are the electric cables 45 of the transmission cable 31, iscovered with an insulation coating. One transmission cable 31 is formedby disposing two sets of the four electric cables 45 on the right andleft sides and in two stages in the upward and downward direction, andbinding outer circumferences of the insulation coatings with an outercover. In a state where the insulation coatings are peeled from fourconductors, the four conductors are formed straight while being parallelto each other. A distal end of the conductor of the electric cable 45 isconnected to the conductor connection part 49 via soldering. Asillustrated in FIG. 20, the image sensor 33 and the transmission cable31 are covered with the molded resin 17. As a result, the conductorconnection parts 49, the conductors, the insulation coatings of theelectric cables 45, and the outer cover of the transmission cable 31 areembedded in the molded resin 17.

As described above, in the endoscope 111 of the nineteenth configurationexample, since the four conductor connection parts 49 can be disposed atthe four corners of the substrate of the image sensor 33, as illustratedin FIG. 22, the four conductor connection parts 49 can be disposed onthe substrate of the square image sensor 33 while spaced equally and themaximum distance from each other. Accordingly, it is possible to easilyensure an insulation distance without causing adjacent two conductorconnection parts 49 to be connected to each other via soldering in asoldering step. As a result, it is possible to easily thin the distalportion 15. As illustrated in FIG. 22, the four conductor connectionparts 49 may be disposed at the four corners of the substrate of theimage sensor 33 in the endoscope 11 of the first embodiment.

Twentieth Configuration Example

As illustrated in FIG. 21, the endoscope 111 of the twentiethconfiguration example includes objective cover glass 91; the sensorcover glass 43; the image sensor 33, the imaging area 41 of which iscovered with the sensor cover glass 43; a lens 93 which is interposedbetween the objective cover glass 91 and the sensor cover glass 43, andthe optical axis of which coincides with the center of the imaging area41; the aperture stop 51 interposed between the objective cover glass 91and the lens 93; the bonding resin 37 with which the lens 93 is fixed tothe sensor cover glass 43; and an air layer 95 provided between the lens93 and the sensor cover glass 43.

In the endoscope 11 of the first embodiment, the bonding resin 37 isapplied to the separation part 47 having a finite width between thefinal lens L3 of three lenses and the sensor cover glass 43, and thus,the lens L3 is directly attached to the sensor cover glass 43. Incontrast, in the endoscope 111 of the second embodiment, the lens 93 isdirectly attached to the sensor cover glass 43 via the bonding resin 37.As a result, in the endoscope 111, the bonding resin 37 hassubstantially a line shape in a side view (refer to FIG. 22). In theendoscope 111 of the second embodiment, both end side edge portions ofthe lens 93 are directly attached to the sensor cover glass 43 with thebonding resin 37. The bonding resin 37 is applied to only the edgeportions.

The lens 93 is a single lens, has the same square columnar exteriorshape as that of the image sensor 33, and has a square section in thedirection perpendicular to the optical axis. Light, which is incidentfrom a subject and passes through the objective cover glass 91, isimaged on the imaging area 41 of the image sensor 33 via the sensorcover glass 43 by the lens 93. A recessed portion is formed in a sensorcover glass 43 side surface of the lens 93. A convex curved surfaceportion 97 is formed on a bottom surface of the recessed portion in sucha way as to protrude and form a substantially spherical surface. Owingto the convex curved surface portion 97, the lens 93 acts as an opticalsensor that converges light. A protrusion distal end of the convexcurved surface portion 97 is slightly spaced from the sensor cover glass43. In contrast, a rectangular annular end surface of the lens 93surrounding the recessed portion is bonded to the sensor cover glass 43via the bonding resin 37. Accordingly, air is sealed in the recessedportion between the lens 93 and the sensor cover glass 43. Air sealed inthe recessed portion, which becomes a sealed space, preferably is dryair. Nitrogen may be sealed in the recessed portion. As such, the airlayer 95 having the recessed portion as an inner volume is formedbetween the lens 93 and the sensor cover glass 43. The convex curvedsurface portion 97 is disposed in the air layer 95. That is, a lightemitting surface of the convex curved surface portion 97 of the lens 93is in contact with air.

An important factor in the thinning of the endoscope 111 having themaximum outer diameter Dmax of 1.0 mm is whether the number of lenses isreduced. Accordingly, in a case where the lens 93 is provided as asingle lens in the endoscope 111, the magnitude of a refractive indexdifference between the lens 93 and a very small area, which ispositioned in a width direction parallel to the direction of the opticalaxis, is important. In the endoscope 111 of the twentieth configurationexample, an air layer is provided on an optical sensor surface such thata large refractive index difference between the lens 93 and the airlayer can be obtained.

As described above, in the endoscope 111 of the twentieth configurationexample, since the recessed portion is formed in the lens 93, the convexcurved surface portion 97 is formed on the bottom surface of therecessed portion, and the rectangular annular end surface is bonded tothe sensor cover glass 43, the air layer 95 for increasing a refractiveindex difference with respect to the lens 93 can be ensured in a verysmall area. At the same time, it is possible to easily align the opticalaxis of the lens 93 with respect to the imaging area 41. Since it ispossible to ensure the air layer 95, it is possible to obtain a largelens power between the lens 93 and the air layer 95. Accordingly, it ispossible to reduce the number of lenses to one in the endoscope 111. Asa result, it is possible to reduce the size and the cost of theendoscope 111.

Twenty-First Configuration Example

FIG. 23 is a side view illustrating an example of the dimensions of theobjective cover glass, the lens, and the sensor cover glass. In theendoscope 111 of the twenty-first configuration example in theembodiment, a thickness TGt of the objective cover glass 91 in adirection along the optical axis, a thickness SRt of the lens 93, and athickness SGt of the sensor cover glass 43 are set to a range from 0.1mm to 0.5 mm. The shape of the objective cover glass 91, the lens 93,the sensor cover glass 43, and the image sensor 33 is a square havingone side length SQL of 0.5 mm. In the image sensor 33 illustrated inFIGS. 20 to 23, an electric circuit 99 with a thickness is illustrated.The bonding resin 37 with a thickness, with which the sensor cover glass43 is bonded to the image sensor 33, is illustrated.

The sensor cover glass 43 acts to hold a distance between the lens 93and the imaging area 41 according to the focal length and the opticalcharacteristics of the lens 93. Since the thickness SGt of the sensorcover glass 43 is set to a range from 0.1 mm to 0.5 mm, the adjustmentthereof is easy.

Since the thickness SRt is set to a range from 0.1 mm to 0.5 mm, thelens 93 is capable of acting as an optical sensor, and it is possible toensure the air layer 95.

Since the thickness TGt is set to a range from 0.1 mm to 0.5 mm, theobjective cover glass 91 can be used alone without the use of otherreinforcement members. It is possible to prevent the reduction of theangle of view caused by the kicking of light beams which results from anunnecessary thickness increase.

As described above, in the endoscope 111 of the twenty-firstconfiguration example, it is possible to prevent the reduction of theangle of view, and to prevent the increase of dimensions from theobjective cover glass 91 to the image sensor 33 in the direction alongthe optical axis while holding an adequate distance between the lens 93and the image sensor 33, and easily ensuring the air layer 95.

Twenty-Second Configuration Example

As illustrated in FIG. 20, the endoscope 111 of the twenty-secondconfiguration example in the embodiment includes the molded part 65, inwhich an outer circumferential surface of the objective cover glass 91apart from an objective surface, an outer circumferential surface of thelens 93, and the image sensor 33 are coated with and are fixed by themolded resin 17, and which forms an outer shell of the distal portion 15and is exposed to the outside; and the tubular sheath 61 that is formedto have the same outer diameter as that of the distal portion 15, coversat least a portion of the molded part 65, and is connected to the moldedpart 65.

As described above, the sheath 61 is made of a resin material havingflexibility. As described above, for the purpose of imparting strengthto the sheath 61, a single cable, multiple cables, a braided tensilestrength cable may be provided on the inner circumferential side of thesheath 61. The tensile strength cable is made of the aforementioned samematerial.

In the endoscope 111, the objective cover glass 91, the lens 93, thesensor cover glass 43, the entire image sensor 33, a portion of thetransmission cable 31, and a portion of the light guides 57 are coatedwith and are fixed by the molded resin 17. The molded resin 17 isexposed to the outside. The distal portion 15 of the endoscope 111 mayinvolve a radiopaque marker. As a result, it is possible to easilyconfirm a distal end position of the endoscope 111 in radioscopy.

In the endoscopes 111, since the objective cover glass 91, the lens 93,the sensor cover glass 43, the image sensor 33, a portion of thetransmission cable 31, and a portion of the light guides 57 (image unit)are coated with and are fixed by the molded resin 17, the number ofinterposed members required to fix the members is small. Accordingly, itis possible to reduce the diameter of the distal portion 15 of theendoscope 111. Also, in a case where a further thinning of the distalportion 15 is attempted, it is possible to configure the distal portion15 with the minimum dimensions. In addition, it is possible to reducecomponent costs. It is possible to realize the endoscope 111 capable ofcapturing an image of a very thin target lesion such as a blood vesselof a human body. As a result, it is possible to reduce the size and thecost of the endoscope 111.

The molded resin 17 is molded so as to cover a region from the imagesensor 33 to the objective cover glass 91, thereby contributing to anincrease in the fixing strength of the image unit. The molded resin 17increases the air tightness (that is, there are not many small gaps),the water tightness, and the light shielding properties of the air layer95. The molded resin 17 also increases the light shielding propertieswhen the optical fibers 59 for the light guides 57 are embedded.

Since the molded resin 17 is molded over the light guides 57, the lightguides 57 act as a structural member in the distal portion 15 of theendoscope 111, and it is possible to improve connection strength betweenthe soft portion 29 and the distal portion 15 in the thin endoscope 111.Since the objective cover glass 91 of the distal portion 15 and the fouroptical fibers 59 are coated with the molded resin 17, when the distalportion 15 is viewed from an insertion side outermost surface (refer toFIG. 19), there is no clearance on the circumference (that is, gap onthe circumference) of each of the objective cover glass 91 and the fouroptical fibers 59 in the endoscope 111. As a result, when the endoscope111 is sterilized (that is, is cleaned) after use in an examination orsurgery, it is possible to reduce the amount of adherence of cleaningresiduals such as unwanted liquid to the endoscope 111, and theendoscope 111 is capable of providing a higher level of convenience fromthe perspective of sanitation when the endoscope 111 will be used in anext examination or surgery compared to the endoscope 11 of the firstembodiment.

In the endoscope 533 in the related art disclosed in WO2013/146091, theaxial line of the distal portion is offset from the optical axis of thelens unit 547. For this reason, a distance to a subject is likely tochange according to the rotational angle of the distal portion, and itis difficult to stably obtain a good quality image. If the axial line ofthe distal portion is offset from the optical axis of the lens unit 547,the state of interference between a duct inner wall and the distalportion is changed according to the rotational angle of the distalportion, and particularly, when the endoscope 533 is put into a thinhole, operability deteriorates. In contrast, in the endoscope 111, theobjective cover glass 91, the lens 93, the sensor cover glass 43, andthe image sensor 33 are coaxially continuous with each other. That is,the objective cover glass 91 is disposed concentrically with the distalportion 15. As a result, it is possible to easily thin the endoscopes111 of the twenty-second configuration example, to stably obtain a goodquality image, and to improve ease of insertion.

Twenty-Third Configuration Example

In the endoscope 111 of the twenty-third configuration example, thethickness of the sheath 61 is preferably set to a range from 0.1 mm to0.3 mm.

The molded part 65 of the endoscope 111 includes the small-diameterextension portion 71 illustrated in FIG. 20 which extends rearward froma rear end covering the image sensor 33. The small-diameter extensionportion 71 is molded into a columnar shape, and the four optical fibers59 are embedded in the small-diameter extension portion 71. Thetransmission cable 31 is embedded in the small-diameter extensionportion 71 while being positioned inside the four optical fibers 59. Theinner diameter side of the sheath 61 is fixed to the outer circumferenceof the small-diameter extension portion 71 with a bonding agent or thelike. That is, the molded part 65 and the sheath 61 are coaxiallycontinuous with each other with the maximum outer diameter Dmax set to1.0 mm.

As described above, in the endoscope 111 of the twenty-thirdconfiguration example, since the thickness of the sheath 61 can be setup to 0.3 mm, it is possible to easily increase the tensile strength ofthe sheath 61. The minimum outer diameter of the existing transmissioncable 31 is approximately 0.54 mm. If the maximum outer diameter Dmax ofthe distal portion 15 is set to 1.0 mm, the thickness of the sheath 61is 0.23 mm. Since the thickness of the sheath 61 is set to the rangefrom 0.1 mm to 0.3 mm, it is possible to set the maximum outer diameterDmax of the distal portion 15 of the endoscope 111 to 1.0 mm.

Hereinafter, a method of manufacturing the endoscopes having theconfigurations in the embodiments (a step of manufacturing a distalportion) will be described. Hereinafter, a method of manufacturing theendoscope 11 of the first embodiment will be described as arepresentative example.

FIGS. 24A to 24D are views illustrating a first example of the endoscopemanufacturing method. FIG. 24A is a view illustrating the configurationof a position adjustment jig. FIG. 24B is a side view when the lens unitis fixed to the image sensor. FIG. 24C is a video when positionalignment in X and Y directions is performed. FIG. 24D is a video whenposition alignment in a Z direction is performed. The X and Y directionsrespectively refer to the rightward and leftward direction and theupward and downward direction illustrated in FIG. 1. The Z directionrefers to the forward and rearward direction illustrated in FIG. 1.

In the first example of the endoscope manufacturing method, a rear endof the lens unit 35 is blocked by and is fixed to the image sensor 33via a position adjustment jig 113. The position adjustment jig 113includes a sensor support portion 115; a first XYZ stage 117; a lensunit support portion 119; a second XYZ stage 1210; a flat platen 1230;and a test chart 1250.

The sensor support portion 115 supports a lower surface of the imagesensor 33. The first XYZ stage 117 holds the sensor support portion 115,and is capable of adjusting the positon of the sensor support portion115 in the forward and rearward direction and the upward and downwarddirection (it is desired to use a macro stage). The lens unit supportportion 119 horizontally supports the lens unit 35 via both sidesurfaces. The second XYZ stage 1210 holds the lens unit support portion119, and is capable of adjusting the position of the lens unit supportportion 119 in the forward and rearward direction and the upward anddownward direction. The test chart 1250 is a subject of the lens unit35. The test chart 1250 includes a pattern which can be referred to forvignetting and the focus of a subject image when an image of the subjectis captured. The flat platen 1230 supports all of the test chart 1250,the sensor support portion 115, and the lens unit support portion 119.

The assembly of the distal portion 15 is performed via the positionadjustment jig 113, and basically, is manually performed by a worker viaa microscope.

First, the bonding resin 37 is applied to at least one of the lens unit35 and the image sensor 33 in advance. With reference to an imagecaptured by the image sensor 33, the optical axis of the lens unit 35 ispositionally aligned with the center of the imaging area 41 of the imagesensor 33 while the lens unit 35 is supported and the image sensor 33supported by the first XYZ stage 117 is moved. Specifically, asillustrated in FIG. 24C, the center of the lens support member 39 andthe lens L3 is positionally aligned with a video center 1270. A video ofthe image sensor 33 is obtained by connecting a probe (not illustrated)to a terminal of the image sensor 33, reading a video signal, anddisplaying an image on the display apparatus (not illustrated).

Subsequently, the lens unit 35 is positionally aligned with the imagesensor 33 in the direction along the optical axis. In a positionalignment step, as illustrated in FIG. 24D, light incident from the testchart 1250 is focused on the imaging area 41 of the image sensor 33 byadjusting the position of the lens unit 35 in the forward and rearwarddirection. That is, as illustrated in FIG. 24B, focusing is performed byadjusting the position of the lens unit 35 in the direction of anoptical axis LC.

When the position of the lens unit 35 is adjusted, the transmissioncable 31 may be or may not be connected to the conductor connectionparts 49. If the transmission cable 31 is not connected to the conductorconnection parts 49, as described above, a probe is connected to theterminal of the image sensor 33, a video signal is read, and an image ofthe subject for test is displayed on the display apparatus.

If the transmission cable 31 is connected to the image sensor 33, anoutput of the image sensor 33 may be processed by the video processor19, and may be displayed on the display apparatus. It is possible toeasily adjust the position of the lens unit 35 and to reduce the lengthof time required for the position alignment step by using the test chart(for example, resolution chart) 125 which is a predetermined subject.

When the position alignment between the lens unit 35 and the imagesensor 33 is complete, desirably, the bonding resin 37 is slightlyexposed between the lens unit 35 and the image sensor 33. If the amountof the bonding resin 37 is insufficient, the bonding resin 37 isinjected between the lens unit 35 and the image sensor 33. A gap betweenthe lens unit 35 and the image sensor 33 is filled with the injectedbonding resin 37 due to a capillary phenomenon.

After the image sensor 33 is positionally aligned with the rear end ofthe lens unit 35, the bonding resin 37 is hardened via ultraviolet lightillumination, and the lens unit 35 is temporarily fixed to the imagesensor 33 with the bonding resin 37. In a state where the positions ofthe lens unit 35 and the image sensor 33 relative to each other in theforward and rearward direction are maintained, ultraviolet lightillumination is applied to the exposed bonding resin 37. If the bondingresin 37 is hardened via the ultraviolet light illumination, the imagesensor 33 is temporarily fixed to the vicinity of the rear end of thelens unit 35. Since the bonding resin 37 is hardened within a short timeof approximately several seconds via ultraviolet light illumination, itis possible to reduce the length of time required for the step. The lensunit 35 and the image sensor 33 which are temporarily fixed together aredetached from the position adjustment jig 113.

Thereafter, the bonding resin 37 is further hardened via a heattreatment, and the lens unit 35 is permanently fixed to the image sensor33 with the bonding resin 37. If the bonding resin 37 is hardened via aheat treatment, the lens unit 35 is firmly fixed to the image sensor 33.

Subsequently, the molded resin 17 is molded over the distal portion 15such that a rear portion of the lens unit 35 and the image sensor 33 arecovered with the molded resin 17. In a molding step, a sealing portionis configured by applying and firmly fixing the molded resin 17 to thelens unit 35, at least the image sensor 33, the conductor connectionparts 49, and a distal end (portion electrically connected to the imagesensor 33) of the transmission cable 31 which are positioned rearwardfrom the rear end of the lens unit 35.

At this time, the molded resin 17 is applied so as to exceed a frontsurface of the image sensor 33 and to cover the rear end of the lensunit 35, and thus, the separation part 47 is reliably blocked. Themolded resin 17 used has a high viscosity to the extent that at leastthe image sensor 33, the conductor connection parts 49, the distal endof the transmission cable 31, and gaps are covered with the molded resin17. For the main purpose of sealing, the molded resin 17 is applied andprevents the infiltration of moisture into the distal portion 15 fromthe rear side of the image sensor 33 and the separation part 47.

The sealing portion may be formed via a resin die so as to easily formthe molded resin 17 into the illustrated shape. In this case, the resindie (not illustrated) is disposed in advance so as to cover a regionfrom the rear end of the lens unit 35 to the distal end of thetransmission cable 31. The molded resin 17 is allowed to flow into theresin die, and is hardened, and the resin die is detached.

Various well-known bonding agents may be used as the molded resin 17.For example, a bonding agent formed of thermosetting resin such as epoxyresin and acrylic resin may be used. In addition, black resin containingcarbon particles is desirably adopted. As a result, it is possible toprevent the incidence of stray light to the imaging area 41 of the imagesensor 33 from the outside.

Thereafter, the distal portion 15 is placed in an environment of 60° C.to 80° C. for approximately 30 minutes. As a result, the molded resin 17covering the image sensor 33, the conductor connection parts 49, thedistal end of the transmission cable 31, and the separation part 47 iscompletely hardened. If the molding step is complete, the assembly ofthe distal portion 15 to the endoscope 11 is complete.

FIGS. 25A to 25E are views illustrating a second example of theendoscope manufacturing method. FIG. 25A is a view illustrating theconfiguration of a camera-mounted position adjustment jig. FIG. 25B is aside view when the lens unit is fixed to the image sensor. FIG. 25C is avideo when position alignment is performed via a second camera. FIG. 25Dis a video when position alignment is performed via a first camera. FIG.25E is a video when position alignment in the Z direction is performed.The same reference signs are assigned to the same members as thoseillustrated in FIGS. 24A to 24D, and duplicated description will beomitted. Similar to the first example, the X and Y directionsrespectively refer to the rightward and leftward direction and theupward and downward direction illustrated in FIG. 1. The Z directionrefers to the forward and rearward direction illustrated in FIG. 1.

In the second example of the endoscope manufacturing method, the rearend of the lens unit 35 is blocked by and is fixed to the image sensor33 via a camera-mounted position adjustment jig 1290. The camera-mountedposition adjustment jig 1290 includes a first video camera-mountedmicroscope (hereinafter, referred to as a “first camera 1310”) whichobserves the image sensor 33 from the front side, and a second videocamera-mounted microscope (hereinafter, referred to as a “second camera1330”) which observes the lens unit 35 from the rear side.

The first camera 1310 and the second camera 1330 are configured in anintegrated manner, and are configured to be capable of capturing imagesof the right and left sides (or, upper and lower sides, front and rearsides) at the same time. Hereinafter, an integral camera is referred toas a “right and left camera 135”. The imaging directions of the firstcamera 1310 and the second camera 1330 are 180 degrees opposed to eachother in a state where the optical axes of the first camera 1310 and thesecond camera 1330 are aligned with each other with very high accuracy.The right and left camera 1350 is attached to the second XYZ stage 1210,and is disposed between the sensor support portion 115 and the lens unitsupport portion 119 of the camera-mounted position adjustment jig 1290.The sensor support portion 115 is supported by the first XYZ stage 117.The first XYZ stage 117, the second XYZ stage 1210, and the lens unitsupport portion 119 are provided on the flat platen 1230. The test chart1250 is attached to the flat platen 1230.

In the camera-mounted position adjustment jig 1290, a parallelismbetween the sensor support portion 115 supported by the first XYZ stage117 and the lens unit support portion 119 is adjusted in advance, andalignment therebetween is performed with high accuracy. In the mountingof the image sensor 33, a bottom surface of the image sensor 33 istemporarily fastened to the sensor support portion 115. In an example ofa temporary fastening method, many fine holes may be provided in thesensor support portion 115, the fine holes may be connected to a vacuumpump, and the image sensor 33 may be vacuum-suctioned.

The assembly of the distal portion 15 is performed via thecamera-mounted position adjustment jig 1290, and basically, is manuallyperformed by a worker via a microscope. First, the bonding resin 37 isapplied to at least one of the lens unit 35 and the image sensor 33 inadvance.

As illustrated in FIG. 25A, the right and left camera 135 including thefirst camera 1310 and the second camera 1330 having the coincidentoptical axis is disposed between the image sensor 33 and the lens unit35. Subsequently, as illustrated in FIG. 25D, with reference to a videocaptured by the first camera 1310, the center of the imaging area 41 ofthe image sensor 33 is moved to the video center 1270. As illustrated inFIG. 25C, with reference to a video captured by the second camera 1330,the center of the lens unit 35 is moved to the video center 1270.Thereafter, after the right and left camera 135 is retracted asillustrated in FIG. 25B, as illustrated in FIG. 25E, with reference to avideo captured by the image sensor 33, a distance between the lens unit35 and the image sensor 33 in the direction along the optical axis isadjusted.

In a position alignment step, the right and left camera 135 (precisely,optical axis of the right and left camera 135) is aligned with thecenter (central position in the radial direction) of the lens unit 35 byadjusting the position of the second XYZ stage 1210 with reference tothe video of the rear end of the lens unit 35 captured by the secondcamera 1330. With reference to the video captured by the first camera1310, the position of the first XYZ stage 117 in the rightward andleftward direction is adjusted, and the center of the imaging area 41 ofthe image sensor 33 supported by the sensor support portion 115 is movedto the center of an XY coordinate on a screen, that is, to the centralposition of the lens unit 35. As a result, even if the center of theimaging area 41 of the image sensor 33, that is, the optical axis LCvaries due to a solid, the lens unit 35 can be positionally aligned withthe image sensor 33 with respect to the optical axis LC which is adatum.

The right and left camera 135 is retracted from a position between thesensor support portion 115 and the lens unit support portion 119, theposition of the first XYZ stage 117 in the forward and rearwarddirection is adjusted, and the image sensor 33 supported by the sensorsupport portion 115 is brought into contact with the rear end of thelens unit 35.

After the image sensor 33 is positionally aligned with the rear end ofthe lens unit 35 in the aforementioned operations, similar to the firstexample, the bonding resin 37 is hardened by irradiating an exposedcoating portion of the bonding resin 37 with ultraviolet light, and thelens unit 35 is temporarily fixed to the image sensor 33 with thebonding resin 37. As such, the image sensor 33 is mounted to the rearend of the lens unit 35 after position alignment.

Thereafter, similar to the first example, the lens unit 35 ispermanently fixed to the image sensor 33 with the bonding resin 37 via aheat treatment. Subsequently, similar to the first example, a moldingprocess is performed, and the assembly of the distal portion 15 to theendoscope 11 is complete.

Third Embodiment

Hereinafter, an endoscope 121 of a third embodiment will be described.

FIG. 26 is a sectional view illustrating an example of a distal portionof the endoscope 121 of the third embodiment. In the third embodiment,the same reference signs are assigned to the same members as thosedescribed in the first embodiment and the second embodiment, andduplicated description will be omitted.

A feature of the endoscope 121 of the third embodiment is that the covertube 69 is not provided. In the endoscope 121, the maximum outerdiameter Dmax of the distal portion 15 is 1.8 mm. The molded part 65includes the small-diameter extension portion 71 that extends toward anopposite side of the distal flange portion 63 from a large-diametermolded body 123.

The sheath 61 has flexibility, and covers the lenses L1, L2, and L3, theimage sensor 33, a portion of the illuminator (for example, light guides57), and the transmission cable 31 so as to protect the distal portion15 of the endoscope 121. The sheath 61 is formed to have the same outerdiameter (that is, maximum outer diameter Dmax) as that of the distalflange portion 63. In contrast, an inner circumferential portion of thesheath 61, which covers the small-diameter extension portion 71, has asmall diameter. An inner circumferential portion of the sheath 61, whichcovers the molded body 123, has a large diameter. As a result, theportion of the sheath 61, which covers the small-diameter extensionportion 71, becomes a thick wall portion 125, and the portion of thesheath 61, which covers the molded body 123, becomes a thin wall portion127. A stepped portion 129 is formed between the thick wall portion 125and the thin wall portion 127 on the inner circumference of the sheath61. The stepped portion 129 is filled with a sheath bonding agent 131.

Similar to the endoscope 11 of the first embodiment, it is possible torealize a further thinning of the distal portion 15 of the endoscope121. Since the endoscope 121 does not require the cover tube 69, it ispossible to reduce the number of components. Since the distal portion 15of the endoscope 121 is soft in comparison with that of the endoscope 11including the cover tube 69 made of metal such as stainless steel (forexample, SUS316), the endoscope 121 is capable of absorbing an impactapplied when the endoscope 121 is inserted into a body or the like.Since the endoscope 121 absorbs an impact well in comparison with thatin a case where the distal portion 15 is made of metal, an operator caneasily perform an operation. That is, it is possible to improveoperability.

Twenty-Fourth Configuration Example

FIG. 27 is a sectional view illustrating an example of the distalportion of the endoscope 121 in which the hardness of the sheath 61differs in a stepwise manner. FIG. 28 is a sectional view illustratinganother example of a distal portion of an endoscope 135 in which thehardness of the sheath differs in a stepwise manner.

The hardness of the sheath 61 may differ according to positions on theinsertion part 21 of the endoscope 121. That is, the sheath 61 of theendoscope 121 includes a distal low hardness portion 133 having a lowhardness on a distal side of the insertion part 21. The hardness ofother portion (that is, a rear end side portion or a portion other thanthe portion on the distal side) further increases in a stepwise mannerthan that of the distal low hardness portion 133. This configuration canbe similarly applied to the endoscope 121 having the maximum outerdiameter Dmax of 1.8 mm illustrated in FIG. 27, and the endoscope 135having the maximum outer diameter Dmax of 1.0 mm illustrated in FIG. 28.

When using the endoscope 121 or 135, an operator inserts the distalportion 15 of the endoscope 121 into an insertion opening (notillustrated) of a catheter acting as an insertion guide. At this time,the operator holds a portion (positioned a predetermined length rearwardfrom the distal portion 15) of the endoscope 121 or 135 with fingers,and inserts the distal portion 15 into the insertion opening. If thedistal portion 15 is inserted into the insertion opening, thereafter,the endoscope 121 or 135 is quickly inserted. The strong holding of theendoscope 121 or 135 has to be prevented from causing damage to theendoscope 121 or 135 for a particularly thin blood vessel. Since theendoscopes 121 and 135 include the distal low hardness portion 133having a predetermined length from the distal end, and the hardness ofother portion (that is, a rear end side portion or a portion other thanthe portion on the distal side) further increases in a stepwise mannerthan that of the distal low hardness portion 133, it is possible toensure operability of and to prevent damage to the endoscopes 121 and135.

The length of the distal low hardness portion 133 may be set to 50 mm to300 mm. If the length of the distal low hardness portion 133 is 50 mm orgreater, it is possible to ensure operability. If the length of thedistal low hardness portion 133 is 300 mm or less, it is possible toreduce a risk of damage.

Twenty-Fifth Configuration Example

FIG. 29 is a sectional view illustrating an example of the distalportion of the endoscope 121 in which the hardness of the sheath 61differs in a stepwise manner, that is, in three stages. FIG. 30 is asectional view illustrating another example of the distal portion of theendoscope 135 in which the hardness of the sheath differs in a stepwisemanner, that is, in three stages. The hardness of the sheath 61 of theendoscope 121 may differ in three stages. In this case, the sheath 61 ofthe endoscope 121 includes the distal low hardness portion 133 having alow hardness on the distal side of the insertion part 21. The distal lowhardness portion 133 is connected to a connection medium hardnessportion 137 having a hardness higher than that of the distal lowhardness portion 133 in a stepwise manner. A high hardness portion 139having a hardness, which is higher than that of the connection mediumhardness portion 137 in a stepwise manner, is connected to a side of theconnection medium hardness portion 137 opposite to the distal lowhardness portion 133. This configuration can be similarly applied to theendoscope 121 having the maximum outer diameter Dmax of 1.8 mmillustrated in FIG. 29, and the endoscope 135 having the maximum outerdiameter Dmax of 1.0 mm illustrated in FIG. 30.

FIG. 31 is a table illustrating an example of hardness values atpositions on the insertion part. In the endoscopes 121 and 135 in whichthe hardness of the sheath 61 differs in three stages, the hardnessvalues of the distal low hardness portion 133, the connection mediumhardness portion 137, and the high hardness portion 139 are preferablyset to ranges illustrated in FIG. 31. That is, the Shore D hardness ofthe distal low hardness portion 133 is preferably set to 25 to 55. TheShore D hardness of the connection medium hardness portion 137 ispreferably set to 40 to 65. The Shore D hardness of the high hardnessportion 139 is preferably set to 60 to 75. If the distal low hardnessportion 133 is softer than a Shore D hardness of 25, a risk of damageincreases. If the high hardness portion 139 is harder than a Shore Dhardness of 75, a risk of damage increases.

If portions of the sheath 61 have different hardnesses, the meltingpoints of the portions are different from each other. In this case, thejoining of both is performed at a high melting temperature. A resinmaterial having a low melting point is heated at a temperatureconsiderably exceeding the melting point. Due to the overheating, sinksor voids are likely to occur in the resin material, a bonding surfacebecomes unstable, and bonding strength decreases. In the endoscopes 121and 135, the connection medium hardness portion 137 is interposedbetween the distal low hardness portion 133 and the high hardnessportion 139. The connection medium hardness portion 137 is capable ofreducing a difference in melting points. Accordingly, in the endoscopes121 and 135 in which the hardness of the sheath 61 differs in threestages, it is possible to prevent the overheating of the resin materialswhen connection is performed.

In the endoscopes 121 and 135, since the distal end has necessarysoftness, a hand side has necessary hardness, and the connection mediumhardness portion 137 is interposed therebetween, it is possible to solvethe aforementioned manufacturing problem (that is, a decrease in thebonding strength of the bonding surface).

Twenty-Sixth Configuration Example

In the endoscope 121, the molded body 123 includes the small-diameterextension portion 71 illustrated in FIG. 26. As a result, the sheath 61includes the thick wall portion 125 and the thin wall portion 127. Inthe endoscope 121, an extension end surface 141 of the small-diameterextension portion 71 is disposed in the thick wall portion 125 of thesheath 61. A cavity 143 is formed inside the sheath 61, and ispositioned opposite to the molded body 123 with respect to the extensionend surface 141.

FIG. 32 is a sectional view illustrating a configuration in which thesmall-diameter extension portion 71 is not formed in the molded part 65.In a case where the extension end surface 141 is not provided in anendoscope, if the sheath 61 is bent, as illustrated in FIG. 32, stressoccurring due to the bending of the sheath 61 concentrates at a bodyrear end portion 145 of the molded body 123. That is, stressconcentrates at the thin wall portion 127. In contrast, in theconfiguration in which the extension end surface 141 is provided in theendoscope 121 illustrated in FIG. 26, the extension end surface 141 isdisposed in the thick wall portion 125, and thus, when the sheath 61 isbent, stress occurring due to the bending of the sheath 61 concentratesin the thick wall portion 125 of the sheath 61. Accordingly, theconcentration of stress at the thin wall portion 127 is avoided in theendoscope 121. As a result, damage to the sheath 61 may not be likely tooccur. This approach is effective in main portions of a particularlythin endoscope in many thin wall members are used.

Various embodiments have been described with reference to theaccompanying drawings; however, the present invention is not limited tothe examples. It is apparent to persons skilled in the art that thepersons can conceive various change or modification examples within thescope of the claims. It is ascertained that the various change ormodification examples are naturally included in the technical scope ofthe present invention. Various configuration elements in the embodimentsmay be arbitrarily combined together insofar as the combinations do notdepart from the concept of the invention.

According to the present invention, there is provided an endoscopeincluding: a single lens having a square exterior shape in a directionperpendicular to an optical axis; an image sensor that has same exteriorshape as the exterior shape of the single lens in the directionperpendicular to the optical axis; sensor cover glass that covers animaging area of the image sensor, and has same exterior shape as theexterior shape of the single lens in the direction perpendicular to theoptical axis; bonding resin with which the sensor cover glass is fixedto the single lens, the optical axis of which coincides with a center ofthe imaging area; a transmission cable including four electric cableswhich are respectively connected to four conductor connection partsprovided on the image sensor; and multiple illuminators that areprovided along the optical axis, and are disposed equally spaced alongan outer circumference of the single lens. The four conductor connectionparts are collectively provided on a surface of the image sensoropposite to the imaging area, and the maximum outer diameter of a distalportion including the single lens and the illuminator is 1.0 mm.

According to the present invention, there is provided the endoscope inwhich the conductor connection parts are respectively disposed at fourcorners of the image sensor.

According to the present invention, there is provided the endoscope inwhich a central portion of the single lens includes a convex curvedsurface on an image side which forms a convex lens surface and protrudesin such a way as to form a substantially spherical surface, an endsurface of a circumferential edge portion of the single lens is a flatsurface, and the entire end surface has a bonding surface with respectto the sensor cover glass.

According to the present invention, there is provided the endoscope inwhich at least a portion of the single lens, the image sensor, a portionof the transmission cable, and a portion of the illuminator are coatedwith and are fixed by molded resin.

According to the present invention, there is provided an endoscopeincluding: at least one lens having a circular exterior shape in adirection perpendicular to an optical axis; an image sensor that has asquare exterior shape in the direction perpendicular to the opticalaxis, and has one side whose length is same as length of a diameter ofthe lens; a sensor cover that covers an imaging area of the imagesensor, has a square exterior shape in the direction perpendicular tothe optical axis, and has one side whose length is same as one sidelength of the image sensor; a bonding resin portion that fixes thesensor cover to the lens, the optical axis of the lens coinciding with acenter of the imaging area; a transmission cable connected to the imagesensor; an illuminator provided along the lens and the transmissioncable; a tubular sheath that covers a portion of the illuminator and thetransmission cable; and a cover tube that covers the lens, the imagesensor, and a portion of the illuminator, is coaxially connected to thetubular sheath in a state that outer circumferential surface of thecover tube is flush and continuous with outer circumferential surface ofthe tubular sheath, and forms a distal portion. The cover tube issmaller in thickness than the tubular sheath, and the distal portionincluding the lens, the illuminator, and the cover tube has a maximumouter diameter of 1.8 mm.

According to the present invention, there is provided an endoscopeincluding: a single lens having a square exterior shape in a directionperpendicular to an optical axis; an image sensor that has an exteriorshape which is same as an exterior shape of the single lens, in thedirection perpendicular to the optical axis; a sensor cover that coversan imaging area of the image sensor, and has an exterior shape which issame as the exterior shape of the single lens, in the directionperpendicular to the optical axis; a bonding resin portion that fixesthe sensor cover to the single lens, the optical axis of the lenscoinciding with a center of the imaging area; a transmission cableconnected to the image sensor; an illuminator provided along the singlelens and the transmission cable; a tubular sheath that covers a portionof the illuminator and the transmission cable; and a molded portion thatcovers and fixes the single lens, the image sensor, and a portion of theilluminator, and forms a distal portion. The molded portion is coaxiallyand continuously connected to the tubular sheath, and the distal portionincluding the single lens, the illuminator, and the molded portion has amaximum outer diameter of 1.0 mm.

According to the present invention, there is provided the endoscope inwhich the tubular sheath has a thickness of 0.1 mm to 0.3 mm.

According to the present invention, there is provided the endoscope inwhich multiple illuminators are provided along the lens and thetransmission cable. Each illuminator is equiangularly disposed in acircumferential direction.

According to the present invention, there is provided an endoscopeincluding: a single lens having a square exterior shape in a directionperpendicular to an optical axis; an image sensor that has same exteriorshape as the exterior shape of the single lens in the directionperpendicular to the optical axis; sensor cover glass that covers animaging area of the image sensor, and has same exterior shape as theexterior shape of the single lens in the direction perpendicular to theoptical axis; and bonding resin with which the sensor cover glass isfixed to the single lens, the optical axis of which coincides with acenter of the imaging area. The image sensor has a diagonal lengthdimension of approximately 0.7 mm. An air layer is provided between thesingle lens and the sensor cover glass. A central portion of the singlelens includes a convex curved surface on an image side which forms aconvex lens surface and protrudes to form a substantially sphericalsurface, an end surface of a circumferential edge portion of the singlelens is a flat surface, and the entire end surface has a bonding surfacewith respect to the sensor cover glass.

According to the present invention, there is provided the endoscope inwhich the thicknesses of the single lens and the sensor cover glass in adirection along the optical axis are set to a range from 0.1 mm to 0.5mm.

According to the present invention, there is provided the endoscopefurther including: a molded part in which an outer circumferentialsurface of the single lens and the image sensor are coated with and arefixed by molded resin, and which forms an outer shell of a distalportion including the single lens and is exposed to the outside; and atubular sheath that is formed to have the same outer diameter as that ofthe distal portion, covers at least a portion of the molded part, and isconnected to the molded part.

According to the present invention, there is provided the endoscope inwhich the thickness of the sheath is in a range from 0.1 mm to 0.3 mm.

According to the present invention, there is provided an endoscopeincluding: a lens unit in which a front group lens and a rear grouplens, which have a circular exterior shape in a direction perpendicularto an optical axis, are accommodated in a lens support member, and anaperture stop is disposed between the front group lens and the reargroup lens; an image sensor that has a square exterior shape in thedirection perpendicular to the optical axis, and has same one sidelength as a diameter of the front group lens and the rear group lens;sensor cover glass that covers an imaging area of the image sensor, hasa square exterior shape in the direction perpendicular to the opticalaxis, and has same one side length as the one side length of the imagesensor; bonding resin with which the lens unit is fixed to the sensorcover glass in a state where the optical axes of the front group lensand the rear group lens coincide with a center of the imaging area; anda rough surface portion that is formed in an outer circumferentialsurface of the rear group lens, and prevents the outer circumferentialsurface from totally reflecting light propagating through the rear grouplens. The diagonal length dimension of the image sensor is approximately1.4 mm.

According to the present invention, there is provided the endoscope inwhich the surface roughness of the rough surface portion is in a rangefrom 0.1 μm to 10 μm.

According to the present invention, there is provided the endoscope inwhich the rough surface portion is formed in an end surface surroundingan image light emitting effective surface of an image side final surfaceof the rear group lens.

According to the present invention, there is provided an endoscopeincluding: at least one lens; an image sensor that has a square exteriorshape in a direction perpendicular to an optical axis, and has the sameone side length as the diameter of the lens; sensor cover glass thatcovers an imaging area of the image sensor, has a square exterior shapein the direction perpendicular to the optical axis, and has the same oneside length as that of the image sensor; a transmission cable connectedto the image sensor; an illuminator provided along the lens and thetransmission cable; a tubular sheath that has flexibility, and coversthe lens, the image sensor, a portion of the illuminator, and thetransmission cable. The sensor cover glass is fixed to the lens, theoptical axis of which coincides with a center of the imaging area, withbonding resin.

According to the present invention, there is provided the endoscope inwhich the sheath includes a distal low hardness portion having a lowhardness on a distal side of an insertion part, and the hardness of aportion other than the portion on the distal side of the insertion partis higher than that of the distal low hardness portion.

According to the present invention, there is provided the endoscope inwhich the distal low hardness portion is connected to a connectionmedium hardness portion having a hardness higher than that of the distallow hardness portion, and a high hardness portion having a hardness,which is higher than that of the connection medium hardness portion, isconnected to a side of the connection medium hardness portion oppositeto the distal low hardness portion.

According to the present invention, there is provided the endoscopefurther including a molded part that covers and fixes the lens, theimage sensor, and a portion of the illuminator, and forms a distalportion. A small-diameter extension portion extending from a molded bodyis formed in the molded part. The sheath includes a stepped portionbetween a thick wall portion covering the molded body and a thin wallportion covering the small-diameter extension portion on an innercircumference of the sheath, and an extension end surface of thesmall-diameter extension portion is disposed in the thick wall portionof the sheath.

According to the present invention, it is possible to reduce the sizeand the cost of an endoscope. The present invention is effectivelyapplied to a thin endoscope or the like used in a medical surgery.

In addition, this application is based on Japanese patent applications(Japanese Patent Application No. 2015-171550, 2015-171551, 2015-171552,2015-171554) filed on Aug. 31, 2015 and a Japanese patent application(Japanese Patent Application No. 2016-076172) filed on Apr. 5, 2016, andcontents thereof are incorporated herein by reference.

What is claimed is:
 1. An endoscope comprising: an image sensor; atleast two lenses including a distal lens and a proximal lens; a sensorcover that covers an imaging area of the image sensor; a transmissioncable that is connected to the image sensor; an illuminator that isdisposed along the lenses and the transmission cable; a tubular sheaththat has flexibility, an inner circumferential portion having a smalldiameter portion and a large diameter portion, the large diameterportion having a diameter larger than a diameter of the small diameterportion, the tubular sheath covering a proximal part of the distal lens,the proximal lens, the image sensor, a proximal part of the illuminator,and the transmission cable; and a flange that covers a distal part ofthe distal lens and a distal part of the illuminator, that is coaxiallyconnected to the sheath in a manner that an outer circumferentialsurface of the flange is flush with an outer circumferential surface ofthe sheath, and that constitutes a distal part, wherein the proximallens and the sensor cover are fixed by a bonding resin portion, and anoptical axis of the lenses coincides with a center of the imaging area.2. The endoscope according to claim 1, wherein the image sensor has asquare exterior shape in the direction perpendicular to the opticalaxis, and has one side whose length is the same as a length of adiameter of one of the lenses.
 3. The endoscope according to claim 1,wherein the sensor cover has an square exterior shape and has one sidewhose length is the same as a length of one side of the image sensor. 4.The endoscope according to claim 1, further comprising; a lenssupporting member that supports the lenses, wherein the bonding resinportion has a light-transmitting property, and fixes a planar endsurface of the lens supporting member to the sensor cover.
 5. Theendoscope according to claim 4, further comprising; a molded resin partthat has a light-blocking property and covers the image sensor and thebonding resin portion.
 6. The endoscope according to claim 1, whereinthe flange has a large-diameter part and a small-diameter part which arecontinuously formed into a cylindrical shape; and wherein an insertionhole for an insertion of the illuminator is provided in thelarge-diameter part which is disposed in a distal side of the distalpart.
 7. The endoscope according to claim 1, wherein the illuminatorincludes four illuminators.
 8. The endoscope according to claim 1,wherein the distal part including the lenses and the illuminator has amaximum outer diameter of 1.8 mm.
 9. The endoscope according to claim 1,further comprising: an intermediate lens between the distal lens and theproximal lens, wherein the flange covers a portion of the intermediatelens.
 10. The endoscope according to claim 9, wherein the flange coversa distal portion of the intermediate lens.
 11. An endoscope comprising:an image sensor; at least one lens; a sensor cover that covers animaging area of the image sensor; a transmission cable that is connectedto the image sensor; an illuminator that is disposed along the lens andthe transmission cable; a tubular sheath that is formed by a flexiblematerial, and covers a proximal part of the illuminator and thetransmission cable; a cover tube that is formed by metal or resin,covers at least a part of the lens and a distal part of the illuminator,and that is connected to the sheath in a manner that an outercircumferential surface of the cover tube is flush with an outercircumferential surface of the sheath, and a flange that is connected tothe cover tube in a manner that an outer circumferential surface of theflange is flush with the outer circumferential surface of the covertube, and that constitutes a distal part, wherein the lens and thesensor cover are fixed by a bonding resin portion, and an optical axisof the lens coincides with a center of the imaging area.
 12. Theendoscope according to claim 11, wherein a thickness of the cover tubeis the same as a thickness of the sheath.
 13. An endoscope comprising:an image sensor; three lenses, a proximal lens, a distal lens and anintermediate lens between the proximal lens and the distal lens; asensor cover that covers an imaging area of the image sensor; atransmission cable that is connected to the image sensor; an illuminatorthat is disposed along the lenses and the transmission cable; a tubularsheath that has flexibility, an inner circumferential portion having asmall diameter portion and a large diameter portion, the large diameterportion having a diameter larger than a diameter of the small diameterportion, the tubular sheath covering the proximal lens, the intermediatelens and a proximal part of the distal lens, the image sensor, aproximal part of the illuminator, and the transmission cable; and aflange that covers a distal part of the distal lens and a distal part ofthe illuminator, that is coaxially connected to the sheath in a mannerthat an outer circumferential surface of the flange is flush with anouter circumferential surface of the sheath, and that constitutes adistal part, wherein the proximal lens and the sensor cover are fixed bya bonding resin portion, and an optical axis of the proximal lens, thedistal lens and the intermediate lens coincide with a center of theimaging area.
 14. The endoscope according to claim 13, wherein the imagesensor has a square exterior shape in the direction perpendicular to theoptical axis, and has one side whose length is the same as a length of adiameter of one of the lenses.
 15. The endoscope according to claim 13,wherein the sensor cover has an square exterior shape and has one sidewhose length is the same as length of one side of the image sensor. 16.The endoscope according to claim 13, further comprising; a lenssupporting member that supports the lenses, wherein the bonding resinportion has a light-transmitting property, and fixes a planar endsurface of the lens supporting member to the sensor cover.
 17. Theendoscope according to claim 16, further comprising; a molded resin partthat has a light-blocking property and covers the image sensor and thebonding resin portion.
 18. The endoscope according to claim 13, whereinthe flange has a large-diameter part and a small-diameter part which arecontinuously formed into a cylindrical shape; and wherein an insertionhole for an insertion of the illuminator is provided in thelarge-diameter part which is disposed in a distal side of the distalpart.
 19. The endoscope according to claim 13, wherein the illuminatorincludes four illuminators.
 20. The endoscope according to claim 13,wherein the distal part including the lenses and the illuminator has amaximum outer diameter of 1.8 mm.